The biggest issue I think is emulation only just started to hit obscure titles recently with paralell rdp and angrylion for the graphics. To add people finally getting away from Project 64 which was heavily prone to timing issues (games running slower/faster than on actual hardware, causing things not to happen the way they should)
Handhelds can probably already handle the popular titles, but obscure titles are still a ways out since handhelds have more issues going to the more accurate engines. Popular titles are usually working through more hackish solutions.