Some of the best leaders tend to be those who don't want the power. The lack of want for it keeps them in check and makes them a fair and just ruler.
While he may say he's just waiting, it's quite likely that there are none better than him to lead them. Lor'themar was left with the role by Kael'thas for a reason - he's a pretty damn good leader. The Sunstriders are all dead, unless Blizzard wants to pull something (and even then, I have a feeling many elves would be against it; where the hell have they been for the past decade while the Sin'dorei have been going through all this shit?).
Other elves, Halduron, Rommath, etc, have hinted that it's time (past time, for some) that he take up the seat of power. It would be a great morale booster, and it would be a good way to advance the story in Quel'thalas.