Making a multiplayer client ain't easy.
Five-MP has already suddenly disappeared after collecting donations (Their site's gone and it seems they haven't tweeted anything since 10 april, which is pretty odd considering the fact that they would normally tweet about them actually starting development).
The fact that MultIV wasn't even able to make a proper stable client for IV after all that time really makes me doubt that they could do it for V, which is even more optimized and builds on IV's codebase to a large degree.
The first GTA V multiplayer won't be made by people who are constantly banging drums shouting that they're gonna make a GTA V multiplayer, it'll be made by those guys that are too busy programming to constantly deal with forums and announcements.