Will third time be the charm for Apple's smartwatch? With Series 1 and Series 2 Apple Watch devices now on sale, thoughts are turning towards what the Cupertino company might be planning next - and here are all the rumours we've heard about it so far.

It's an interesting time for wearables in general, with the likes of Fitbit, Samsung, and Google (and its partners) still pushing hard with the idea of smartwatches that let us do all kinds of clever tricks from our wrists. Will the Apple Watch Series 3 be worth waiting for?

The Apple Watch story so far

It's difficult to forget the standing ovation Tim Cook got in September 2014 when he unveiled the original Apple Watch on stage for the first time - this was something the tech world had been eagerly anticipating for years.

The smartwatch went on sale the following April, so really we've had less than two years with the wearable up to this point.

We then got a hardware refresh in September 2016: the new and improved Series 2 model was joined by a Series 1 edition that was basically the original watch with a slighter faster processor inside.

The Series 2 is also a touch faster than the Series 1 and comes with extra features such as built-in GPS and waterproofing, so you can take it for a swim.

In the meantime we've seen a succession of software updates adding more bells and whistles to the watch and generally optimising performance along the way.

That leaves the stage set for an Apple Watch Series 3 edition - but what will it look like, and when can we expect to see it?

The Apple Watch Series 3 - launch date

Considering Apple only just unveiled the Apple Watch Series 2 last September, it would be unexpected if the company came out with anything new before September 2017. The launch date could slip to March or April 2018 - this was when the first watch went on sale, even if it was announced months beforehand.

It's still not certain though that Apple wants to bring out a new smartwatch every year - do people want to upgrade their watches as often as their smartphones?

A September event is guaranteed so that Apple can show off the next iPhone, so it's definitely a possibility as far as the Apple Watch Series 3 goes - the first model was announced alongside the iPhone 6 after all.

Part of the problem is we've only seen two launches so far, so there aren't many clues to go off. The Apple executives themselves might be waiting to see how the Series 1 and Series 2 sell before committing to a date for the next iteration.

It does seem certain that there will be an Apple Watch Series 3 though - Apple has given no indication that it's thinking about giving up on smartwatches just yet.

The Apple Watch Series 3 - rumoured features

With the Series 2 watch featuring a waterproof case and built-in GPS, two of the must-have features for smartwatches have already been ticked off by Apple, but there's still likely to be plenty more to come with the Series 3.

One of the early rumours about the Series 3 is that it's going to be much thinner, with the haptic motor moved to the strap - that's based on a patent filed by Apple.

The Asian outlet DigiTimes, which has an up and down record as far as Apple rumours go, reckons the watch is going to be launched later on in the year. Apparently Apple's focus this time around is battery life, and we'll see few changes in terms of the design.

There have been whispers of a bump in on-board storage, so there's more room to sync music to the watch, and then there's the feature we're all waiting for - full independence from the iPhone, so you can use it as a standalone device.

It seems unlikely that will come with the Series 3, but it might get a little bit closer.

The Apple Watch Series 3 - software

As we mentioned above, software updates have kept pace with the refreshed hardware, and we're now up to watchOS 3. In some ways, with very small bumps on the hardware side, the software is more important as far as Apple's smart timepiece is concerned.

Apple updates all of its software on a pretty regular schedule now, with improvements previewed in the summer at its Worldwide Developers Conference (WWDC) and then the software itself pushed out in September - that means watchOS 4 would arrive alongside the next iPhone and perhaps the Apple Watch Series 3 later this year.

With watchOS 3 still very much the current OS, and still getting updates, we haven't heard too much about what we can expect from watchOS 4, but there's definitely still room for improvement on the software side.

An always-on, low-power time display mode (like the one Android Wear has) is a possibility, but this might depend on how well Apple can improve the battery life on the hardware side.

Other good bets are apps for podcasts and Notes, which don't have native Apple Watch apps yet, plus the usual round of new watch faces for the device.