No, I've got my SI capped out, my smuggler just hit 50 but still has class and world quests to wrap up on Corellia. I still haven't hit Illium with either of them. Just popping off some of the assorted bonus missions and wotnot. Hoth, Voss, Corellia...
I've got a Jedi Knight in the low 30's on Alderaan. I just spent a chunk of the evening running my Bounty Hunter through Dromund Kaas and there was a planetary population of around 30-45, the majority of which were in the 11-17 range.
And I've got a Sith Marauder who's 11th still lurking on the Imperial Fleet...
From what I've seen, I have to say that Corellian Run seems to be pretty balanced in population Republic / Imperial wise.
Heh, now that you can email between your characters without concern for Republic/Imperial wise.. I have to say it's being a little surreal how my smuggler say is picking up materials and level 5 c ompanion gifts, then sending them to the Imp characters who craft stuff then can be used to send those finished products to the Republic side.. (bad roleplaying I know..but hey..it's one of those funky things).
That and my Guild is established on both sides so there's that sort of trade between the guild banks.