It will probably be a mix of A-A and A-G weapons, though I doubt that every single missile will get an AFM, much the same way that JDAMs never received an AFM in DCS while the other bombs got them.
1. Yes, although it was developed specifically for FC3, you will receive the upgrades in World as a patch, for free.
2. The server does not have to own FC3 for AFM missiles. The missile upgrade will come in a patch to the world structure, free of charge, when FC3 comes out. Unknown if the Ka-50 will receive AFM missiles, but at this point it seems likely that at least some of them will get the treatment (e.g. probably for the Vikhrs, but probably not for things like the Kh-25ML (though this is a Su-25T weapon also, so it is possible)).
3. You still get the World specific upgrades that FC3 promised, and will still be able to put FC3 planes in the mission, but only people who own FC3 will be able to fly them around.
Doubtful. From the looks of it, peoples' patience is wearing thin for this franchise, and from where I stand, plus seeing ED's and TFC's opinions on the matter, I can safely say that this is probably the end of the road for the FC series as far as new products goes. needless to say though, it will benefit from continued updates to the World structure.