everyone who plays a lot of online multiplayer is getting better, and the difference of player skill is getting smaller as a whole, so the matches are becoming more competitive and interesting. Newbies entering into 5v5's upset the cart more then ever now, need to have two newbies on other teams as they are so far behind the curve.
As for the details, small changes here and there but entrenchment still has had the biggest influence on multiplayer, diplomacy adds a few nice upgrades but aren't nearly as important as fleet spam and good micro.
Look to rebellion for any major sweeping changes to the multiplayer version of the game.
