Well... level 20 or 50? It depends, so let us get rational.
With so many levels to gain as 50, and I talk out of knowledge of some TSL structures, we could get several options to consider.
More feats and powers. With more feats and force powers, combat would really get more diverse and fun, and they could have higher level requirements for perfectionists around. Are there enough feat and power adds for this? So we would have always something to raise up in 49-50.
Leveled creatures. I think this would be great, which meant no "easy cakewalk" in whatever level you are. Creatures stats could be calculated to match your character in some way. Or AI instead. Or just in special areas. Something.
It's all in proportion.
By the way, why level limit? Because level raise is xp-exponential, I think that evolving chars could only be done 1-50, and up there you would only gain level just as rank and not godlike Hp and Fp, which would only give and idea of playtime with a char.
Thats all folks!