Apps don't expire like milk. It just means they won't be putting out new stuff on those platforms, and won't provide help with what's already out there in the marketplace.
Also, while it is possible to make WP8 compatible with other handsets, if there's no real money to be made in this venture, it's not going to be rolled out by MS.
FWIW, other than the built in storage & RAM, the specs are quite similar between those handsets.
now that nokia has decided to stop app support on sybian and meego,what does it mean:does it mean that a lot of apps will expire or that ur phone will crash.........but cant wp8 b somehow install in some of this high end meego/symbian devices like N9,it would b nice at least N9's speccs outweighs the likes of the lumia 520 to say 920