when 8vs8 or 16vs16 room available?

Since 4vs4 bring more competitive atmosphere, when players can rumble and have fun with a lot of pvpers? Will it possible for patch 2.1a or 2.1b?

I wouldnt expect it.

8v8 is supposed to be Frontlines, the objective based PvP I believe. Don't remember where I read that though.

Considering PvP launched less that a week ago I'd let them see how well this even works out. Getting very very ahead of yourself.