I talked to Lead Designer Damion Schubert about Legacy Level 50 and potential rewards, and here's what he said:
We are currently looking at things we can add to the Legacy page - in particular, Legacy will need some juicing up after the Cartel Market goes live - but I wouldn't expect any changes until after the Free-to-Play update at least.
It would be nice if at legacy 50 there was a perk allowing you to get a bunch of exp from class quests so world quests became optional. Most of us at legacy 50 have done all the world quests several times over.
I want to see the storys of the 2 classes I haven't seen yet but the thought of doing the world quests again just makes me log off.
I totally agree, having to do the world quests over and over is a PAIN! and one of this game's greatst weakness.