[Sony Xperia T, TL, TX, V] Entropy512:
TL developer support is going to highly depend on the bootloader locking situation.

As I understand it, AT&T has a bad habit of forcing bootloader locks. I refuse to support any device that has a locked bootloader which is not officially unlockable - even if the lock gets broken unofficially, it's the principle of the thing.

Yeah. The Infuse was a less popular device, and as a result, the developer community was highly cooperative for a while. Unfortunately, the device itself was a nightmare to work with so it was ditched by many. Although, interestingly enough, now that some of the worst aspects of this device development-wise have been identified, the Infuse is becoming kind of fun to work with again. :)

In the case of the T - all evidence seems to indicate that it's going to be a highly pleasant device to work with, AND if it's not a super-popular device, it may have a more pleasant development community than some of the more popular devices.

There's an existing well-established team of developers with Sony experience, AND there are also a number of Samsung Exynos refugees that have already made the jump or (in my case) are just waiting to see what their local version of the T has to offer.

That said - based on the developers I've seen hopping over, things are going to be heavily weighed in the AOSP-based firmware side of things. Sony's recent devices have become very attractive to developers of AOSP derivatives due to:

Sony's cooperation with the community in terms of technical information and source releases (see DASH)

Most Sony devices are based on Qualcomm chipsets, and over the past year, CodeAurora has emerged as a high quality reference codebase. (CAF has existed for a long time, but it's not really until this year that I saw people using it heavily.)

Sony's explicit AOSP support, both in terms of binary releases to support JBQ's Xperia S project, and frequent commits to AOSP. In fact, they have one developer working part-time on the AOSP Xperia S tree!

However, going back to Snow_fox's comments - if you want a device that is guaranteed not to be dropped early, purchase a Nexus. With any non-Nexus device, you are always taking risks.

Look at the Samsung Exynos situation - A year ago, Samsung devices were looking like your best bet for ongoing developer support. However, over the past year, a variety of things have changed:

Samsung constantly releases broken HALs that require all sorts of workarounds, and don't play nicely with backwards-compatibility solutions that work on other devices. ICS and JB bringup on Exynos4 devices has been an utter nightmare, leading to the entire team of CM on Exynos devices burning out or coming damn close to it

Samsung decided to use their phones as an outlet for gigantic batches of defective eMMC flash chips. They put workarounds in their firmware but didn't tell anyone. The end result is that you have to tread carefully with any 2011-model Samsung device. Their poor handling of the eMMC disaster has left a sour taste in many developers' mouths.

As a result, many developers are leaving, not necessarily for a device that is flashier, but one that is at least more developer-friendly. I think that in many cases, the Xperia TL will be a downgrade for me compared to my Galaxy Note... But dealing with the Exynos in the Note is driving me utterly insane.