Apple Watch Series 4: Rumored specs, price, release date

The Apple Watch debuted back in 2015, and in the three years since it's become the top watch on the market. But it's also kept a pretty similar-looking design. Updates have included GPS and full swim-ready water resistance in the Apple Watch Series 2, and onboard cellular connectivity in Apple Watch Series 3.

The next version could finally be where Apple makes some bigger changes in how it actually looks -- just in time to go up against a brand new Google smartwatch and an imminent Samsung Galaxy Watch. It looks like the smartwatch battle will be more heated in 2018 than ever.

WatchOS 5, unveiled at Apple's WWDC developer conference in San Jose, brings a number of fitness improvements to the table, an instant watch-to-watch walkie-talkie mode, support for podcasts and an ability to play audio from third-party apps on the go.

This is what we think we know so far about the next Apple Watch, and what it might feature. We'll keep updating this with the latest rumors and reports.

Likely release date: September

Apple's last few iPhone events have all fallen around the week or two after Labor Day, and the Apple Watch has appeared alongside the iPhone the last two years. The Apple Watch Series 2 and Series 3 became available a week after both events, and it's a good bet Apple will continue the trend.

Price? Expect more of the same

The Apple Watch has dropped a bit in price over the last few years, but the Apple Watch Series 3 starts at £329, which seems like a logical territory for a next-gen model. A cellular version, just like Series 3, would cost more.

A bigger display

A spring report by analyst Ming-Chi Kuo (who's had a great track record on Apple rumors) says the next Apple Watch will have a 15 percent larger display. The existing Apple Watch models all have a fair amount of bezel that's kept hidden by the smartwatch's black borders and mostly black OLED readouts, but going for a more edge-to-edge look would make sense and open up more room for information and messages.

New solid-state, click-free buttons

Part of the next Apple Watch's slimmer size could be due to a redesign of the clickable side button and spinning clickable digital crown. A recent report from Fast Company says that these buttons will be solid-state, with a phantom haptic-enabled click sensation much like the iPhone 7 and iPhone 8 home buttons and recent MacBook trackpads. The Taptic Engine on Apple Watches are already extremely refined, and making these buttons solid-state could also help the watch be more water resistant.

Always-on Siri, perhaps?

Apple's latest MacBook Pros have added T2 chips that offers always-on Siri. Google's upcoming next wave of Wear OS smartwatches co-developed with Qualcomm promise always-on Google Assistant, too. Would the next Apple Watch possibly have always-accessible Siri without needing to raise up the Apple Watch or press the side button? For accessibility purposes, it could be an appealing pitch... but it would require improved battery life or a more efficient set of processors.

Better battery life?

In the updated design, a larger-capacity battery (with better battery life) might fit. Or, maybe, the next Apple Watch will just be more efficient in using that battery. Part of that better battery life could theoretically come from new display tech: a Bloomberg report in the spring said Apple would be making its own MicroLED displays in future products. MicroLED tech seems to have benefits for wearables, making "slimmer, brighter, less power hungry" gadgets. Better battery life would be a welcome feature for a new Apple Watch: current Apple Watch models typically need daily charging.

A slimmer size, or the same?

The Apple Watch has had nearly the same look for three years: a bit bulbous, with rounded square edges. The changes in design reported so far don't clearly indicate how much thinner it would be, or even if the watch could get larger. Maybe, like iPhone design refreshes, the Apple Watch Series 4 will end up staying similar in size but gaining extra performance, battery and screen size.

Sleep tracking?

A missing feature in WatchOS 5 is built-in sleep tracking on the Apple Watch. Apple acquired sleep-tracking company Beddit in 2017, but hasn't incorporated sleep tracking into its own products or software yet. There are third-party Apple Watch apps that can monitor sleep, but current watch models also typically require nightly charging that gets in the way of the required nighttime wearing needed for sleep analysis.

Fitbit's watches, meanwhile, last around four days on a single charge, making sleep tracking easier. Garmin's smartwatches are adding improved sleep tracking, too. Fitbit's heart rate studies are exploring testing for sleep apnea as well, which could be another target for Apple via improved heart rate sensors. Perhaps Apple figures out a way to have the watch enter a low-power sleep mode that could still measure heart rate and sleep.

Improved health sensors

The Apple Watch already measures heart rate well, and Apple's Heart Study app already recognizes atrial fibrillation using the sensor. Third-party EKG wrist bands like Kardia have added medical-grade heart rate monitoring. Reports going back to last year have suggested Apple could develop blood glucose monitoring tech, although whether that could end up taking the form of a band, an accessory or an onboard sensor remains unclear. Measuring for blood pressure or blood glucose monitoring would likely involve a specialized sensor or band, like what Omron is pursuing on its own watch. Or, perhaps, FDA clearance for additional features using heart rate might be unlocked.

Could there be smart straps?

Recent Apple patent filings for connected watch band accessories could offer extra features like increased battery life. Or, UV exposure sensing. What about blood glucose monitoring, or EKG heart rate measurements, or even blood pressure cuffs? Smart strap rumors have been around since the Apple Watch first debuted, and patent filings are hardly an indicator of imminent product features. Pebble tried developing smart straps for its smartwatches years ago, but nothing ever became of the effort. Will this Apple Watch bring the idea back? It seems unlikely, but keep checking this space.

What about a watch face store?

Despite reports suggesting that iOS 4.3.1 had what looked like support for third-party Apple Watch faces, Apple's preview of WatchOS 5 at WWDC didn't reveal a watch face store. That doesn't mean it couldn't still happen. Maybe debuting new watch faces alongside a new Apple Watch would be the better move. If the next watch also has larger screen sizes, it could also impact how future watch faces are designed.

And, maybe, finally, AirPower

Hey, remember AirPower? Apple's proprietary spin on contactless charging was supposed to offer faster charging for multiple Apple devices like iPhones, AirPods, and even the Apple Watch. According to Apple, the Apple Watch Series 3 is already AirPower-ready (although AirPower isn't here yet). If AirPower exists, it'll likely drop alongside the next iPhone and Apple Watch (and AirPods).