Shawn had indeed agonized over it for a long time.
There were reasons to stay, and reasons to leave.
If he stayed, Shawn would not only have the powerful backing of Shandris Feathermoon, but would essentially have Dire Maul as his own territory.
What? Dire Maul belonged to the Night Elves, and Shandris Feathermoon was its ruler? Heh, as Shandris's one and only nephew, wasn't everything she owned practically Shawn's? Who would dare give him trouble?
Besides, there were so many books here, enough to keep Shawn reading for ages. Deep down, after all, he still liked being a handsome young man quietly reading his books.
If he left, he could continue studying magic under Aegwynn. With his incredible cheat, the Space Garrison, and personal instruction from humanity's greatest mage, Shawn felt his future was bright. And if he continued helping Varian Wrynn, he could keep building favor with a whole host of important figures: Varian Wrynn, Prince Anduin, Jaina, Regent Bolvar, Marshal Windsor, Broll Bearmantle, Valeera, and more. That would be enormously helpful when he traveled across Azeroth in the future.
Oh, Onyxia was destined to be killed. If I take part in the dragon-slaying operation, I should get a share of the spoils at the end, right? Every part of Onyxia is a treasure!
Besides, I still have that sword forged by an ancient dragon, the Unfired Ancient Blade. Once it's tempered, it'll be another rare piece of purple Epic Equipment... Even if I can't use it, it'd make a pretty good gift.
So, after careful consideration, Shawn decided to leave with Aegwynn after all.
After a brief farewell, Shawn teleported to Theramore with Aegwynn.
Before long, the two of them met Jaina.
Only then did they learn that, during their absence, Jaina, Varian Wrynn, Broll, and Valeera