I think that, for now, there are enough planets and moons to keep me entertained for a long time. However there are a few things I'd like to see in the upcoming updates: Docking (can be done with mods for now but official support would be nice) More scenarios with some incentive to complete them, perhaps you unlock new stock parts/kerbonaut or it provides in game currency. Which leads me to my next point... I'd like to see the Career mode evolve a bit. Implement the in game currency/unlocking parts/buying kerbonauts/taking mission contracts etc. I know these are probably not realistic hopes for the next mod but I don't expect them all. I'd just like to see a few of them.
To hell with your "mod", making things easier! Real men use a protractor. Just kidding, the mod's actually really helpful when combined with the interplanetary guide.