I can’t find a straight answer for compatibility issues between WP7 and new WP8.
For example: what if some popular apps like facebook, twitter will be updated to WP8? Will they still work on WP7 (7.8)? Or the latest WP7-compatible version will stay in Marketplace for WP7 users and new fo WP8 will be just for WP8 users?
I’m asking because many of my friends are interested in buying Lumia 800 in great price, but they worried about limited number of apps in future.
Cheers!
Exactly. And developers can continue to update the WP7 version of an app even when a WP8 version has been published.