I am interested to see how the corvettes factor into combat. Not much has been said about them, so I wonder what role they will fulfill. We know they are more of a harassment and support unit, but that doesn't mean much.
I also want to see how these new capital ships operate. I am afraid they may become a rush cap because they can take over enemy ships, but we will see. There is a counter to everything. The devs are also polishing it up so these new ships will probably have an inherent weakness.
Pirates will probably end up not attacking either player and either falling back to neutral status or fall under the control of the first faction to research it. I get that pirates will not be much threat to the Rebel TEC due to their higher offensive style unless they are used in a guerrilla attacks.
First race I will be playing as: Advent, probably Rebels. Advent have so many fun abilities and hopefully they become more powerful economically. Their planets automatically spread culture though, which could become a real pain. That said, it sounds like all the races will be fun to play as now.