Windows Phone 8 is over a year old now, yet we still know very little about Windows Phone 9.

Originally it was expected to be with us by the end of 2013 as it was thought that Microsoft may adopt the annual software cycle made popular by Apple in an attempt to keep its mobile OS fresh and, more importantly, relevant.

That didn't happen, but from the information that we've been able to gather so far it looks like Windows Phone 9 could be a massive overhaul, so it's not surprising that it's taken over a year.

Before 9 however it looks like we're going to get Windows Phone 8.1. Microsoft looks set to announce 8.1 at its Build conference in April 2014, while further leaks highlight that Windows Phone 8.5 may also be on the cards.

Before we get our teeth in Windows Phone 9 we need to visit the rumors surrounding versions 8.1 and 8.5. They have been confused with the ninth iteration of the platform before, and it's important to make a distinction between all three.

Windows Phone 8.1

Windows Phone 8.1 might just be a small number update in name but it looks like it's going to include a lot of new features. The most exciting of those is Cortana. It's a personal assistant along the lines of Siri.

Like Siri or Google Now, users will be able to use text or voice to communicate with Cortana and will be able to use it to search the web, ask for directions, set reminders and a whole lot more.

Cortana

So far so familiar, but to stand out from Google Now and Siri, Cortana will also apparently show emotion when speaking and the way it speaks will vary depending on what you've asked it, just like a real person, bringing us one stop closer to the movie 'Her.'

Cortana will also learn more about you over time, keeping track of things like your address and your interests, allowing it to make its assistance more personal. But if you've got privacy concerns there's no need to worry, because what you allow Cortana to remember is totally under your control.

In terms of other features it looks like a notifications center is in the works. You'll get to it by swiping down from the top of the screen, much like on Android, according to unnamed sources cited by The Verge.

Apparently a short swipe will bring up quick settings, while a longer swipe will reveal the most recent notifications.

Action Centre

According to the first leaked screenshots, the notifications center will actually be called 'Action Center'.

Other possible Windows Phone 8.1 features include fingerprint scanning capabilities, though of course you'll still need a phone with a built in fingerprint scanner in order to use them.

It also looks like users will be treated to a Swype-like keyboard, allowing you to slide your finger between letters rather than tapping.

Live tiles are set to get a bit more, well, live too, as rather than updating once every 30 minutes like they do now, Windows Phone 8.1 will apparently allow them to update as much as once a minute.

Speed dial is a long overdue feature which is apparently being added, if a video shared by Unleash the Phones is to be believed. The same video also showed that Internet Explorer is being updated to version 11, the Calendar app is getting week and year views added and there's a dedicated Podcasts app.

We're also expecting to see support for on-screen buttons, the ability to change your default messaging app, VPN support, separate music and video apps and a change to the way multitasking works, with the back button sending an app into the background rather than closing it.

Rounding out the expected features there's Bluetooth 4.0 and Bluetooth LE support, dual-SIM support and the ability to save apps to microSD cards.

As we've said, Windows Phone 8.1 is likely to be officially unveiled at Microsoft's Build conference in April.

Windows Phone 8.5

It looks like there might also be such a thing as Windows Phone 8.5 in the works, but details are slim on the ground. All that's really known so far is that there will seemingly be some potentially quite substantial changes to the Start screen interface in Windows Phone 8.5, but there's no word yet on what form those changes may take.

It's also worth noting that while we list this as a Windows Phone 8.5 feature and the stuff above as Windows Phone 8.1 features it's entirely possible that some of it may end up in other releases of the OS, so for example the Start screen changes that we're hearing about in Windows Phone 8.5 may not actually emerge until Windows Phone 9.