Despite earlier expectations, there's been no evidence in the leaks from the Windows Phone SDK DevPreview to suggest that Windows Phone will be getting new Live Tile sizes, although this could change before the consumer release. The obvious candidate would be the addition of an extra large square Live Tile size (i.e. double the size of the current double wide Live Tiles).
However, a leak from the SDK documentation does indicate that Windows Phone 8.1 is getting a "new world of tiles and notifications" and that "tiles are cross platform [with Windows 8]". A link to MSDN page, included in the documentation, suggests that developers may be able to take advantage of a large number of "new" cross platform Live Tile templates.
The developer of TimeMe; an app that shows shows the current time, date, weather and current battery level on a single Live Tile; noted in a recent development post that Windows Phone 8.1 supports "1 minute background updates" which allows third party app Live Tiles to be updated more frequently that the current every 30 minutes time period. This would, potentially, address the issue of Live Tile sometimes being behind the times and/or showing out of date information.
We've not been able to confirm precise details on whether this new Live Tile update frequency will apply in the consumer release of Windows Phone. There are some obvious impacts on battery life from more frequent updates and Microsoft will want to avoid having apps that drain the battery unnecessarily. However, our understanding is that this is part of a wider reworking of background processes in general and that this will include changes.
Aside from any implementation changes, it is also important to note that Live Tiles will existing along side a new notification centre, dubbed Action Centre by Microsoft, which means users will essentially have two ways of receiving / seeing out-of-app information about events and notifications.
Windows Phone 8.1 will also improve the platform's multi-tasking experience with changes to background tasks functionality. Our coverage of earlier SDKs leaks mentioned one of these in the form of support for geofencing (carry out a task when your phone enters into a predefined area, such asarriving at work or drawing near to a train station), but there will also be other new features.
For example, it will possible for developers to set a background task for their app to be triggered by a greater range of events / occurrences. These include triggers related to Buetooth, incoming chat messages, changing connection status, operator related activities (including presence of WiFi hotspot), incoming (raw) push notifications, smartcards, the aforementioned location, system events, and more.
This is a key change because it allows for much smarter background task activation and opens up a new range of app experiences. For example, a transit app might be able to integrate smartcard triggered mobile ticketing while in the background, or a Bluetooth LE accessory app could carry out a task in response to a message from a connected accessory (fitness trackers, smart watches) while in the background.
To go along with this richer background task functionality developers will also get improved programmatic access to the status of background tasks (and information about them). Again, this will make it easier for developers to create rich app experiences (e.g. provide information about why something has failed to update in the background).
More generally, what we expect to see, once developers have updated their apps to take advantage of the new features, is more Windows Phone apps that update information or carry out tasks in the background. This might be as "simple" as ensuring information is update to date (e.g. social networks), but may also include "smart" app behaviour, similar to the background location tracking used by some exercise tracking apps in the current version of Windows Phone.