The Third Game in the Game Series Formerly Known as Diablo

I'm sure you can still make a p2p connection with your friends without going through battle.net and play for free if they require payment for battle.net. If nothing else, I'm sure it'll have a LAN multiplayer option and people will use a virtual LAN program. Actually, you're right. If battle.net requires payment, Blizzard will lose a bunch of money because people will do multiplayer by virtual LAN and won't need a unique CD key.

Unlikely. While that sounds good as far as being able to play multiplayer, an economy would not exist, and getting really good items would be a lot harder than if you were on battle.net.