FUD Zilla reports Android 5.0 will limit backward compatibility as Google plans to alleviate fragmentation issues by imposing higher hardware requirements:
Enter the Google tablet. It is expected to ship with ICS in a couple of months and it will be the first device to receive a Jelly Bean update. Contrary to some previous reports, Google’s new tablet will rock a Tegra 3 chip and one of the reasons Google did not go for a cheaper Qualcomm processor is, you’ve guessed it, Jelly Bean. As a result the tablet will end up a tad pricier than $149, probably $199 to undercut Amazon’s Kindle Fire. With this in mind, going for a cheaper CPU that would not offer a proper Jelly Bean experience was not an option for Google.
While a more conservative approach to Android updates would help speed up development, by simply cutting off antiquated devices and imposing drastic hardware requirements, it will undoubtedly make quite a few users very cross indeed. Basically only the fastest, high-end devices will get Jelly Bean, at least officially. Consumers who did not spend $400 or $500 on a high-end Android phone sometime in the last quarter or so can pretty much forget about Jelly Bean. The only way of making sure you will be covered is to get a pricey superphone, based on the S4 or Tegra 3, or upcoming A15 chips.