at facebook road map you can see this link
Old REST API methods will be deprecated at the end of 2010, so what about existing facebook apis that are using Rest api.
Also it says, it won't allow any more fbml applications, does that mean fbml itself will be deprcated (I mean the fbml scripts itself), or they just force us to use Iframe canvas instead, and fbml scripts are still supported?
Thanks in advance.
Deprecation means you will no longer see any updates or recieve any support for those features. They will continue to exist to allow 'legacy' applications not to break. However, if you don't update you may see some breaking changes to other aspects such as a authentication. I would recommend taking the time to upgrade to the latest APIs.
FBML will continue to work but no support will be given for it. After 2010 the FBML option will no longer exist in the application management and I'm sure if you were to edit some application settings you would run into issues