Those of you that rely on the Facebook app for your chats won’t be able to much longer if Facebook follows through on their plan. Facebook has notified users in a few European countries that messaging friends in the Facebook app will stop in about 2 weeks. Users will still be able to message their friends, but they will have to download and install the Facebook Messenger app in order to do so.
This doesn’t appear to be a “test” and is the long term plan for Facebook. You can expect this change to hit every country, but there are a few caveats. Those with lower-end Android devices won’t be required to use Messenger. Also, for whatever reason, Windows phone users will still be able to see messages in the Facebook app. Finally, the Paper newsreader app (not on Android yet) will still show messages.