While there hasn't been much talk about it, IMO the change that will have the biggest impact on how the game is played and the one I've been looking forward to the most is the Warp Speed Changes.
Make no mistake, the warp speed changes are going to have a profound effect on everything from the ships we fly while soloing to fleet composition, strategy and tactics. Smaller, faster ships are going to become even more popular and Battleships will just be bricks with guns that nobody wants to fly very far in.
Interceptors will be extremely popular. EW frigates are getting some serious buffs too but IMO they'll be overshadowed by interceptors. What it boils down to is most players are going to want to fly interceptors rather than EW ships.
It'll be interesting to see how RHMLs work out too. They sound great in theory and would likely be quite popular on battleships except battleships themselves are probably going to be less popular due to increased warp times. I can see them being useful on Black Ops battleships and maybe in capital fleets as an anti cruiser/BC screen too.
Rhavas has a comprehensive article on the Rubicon changes over at Interstellar Privateer. His writeup is extremely good, a must read if you're at all interested in the Rubicon changes.
I'm probably a little biased with this next one since I like Prowlers so much but I liked Nosy's article on Prowlers in Rubicon too.