Here are the possiblities - it's either going to be a new flashy director we haven't heard of yet or it's going to be an already established action movie director, but not that famous - The recent trendy Spanish directors and David Fincher are too serious and dark for Spiderman; Spike Jonze, Terry Gilliam, and Michael Gondry are too wacky; Terrnier is doing the next Hulk; Snyder is doing Watchmen; Tim Story is gonna be with FF4 flicks; Mark Steven Johnson, Burton, Shumaker, and Goyer probably won't be hired again to direct superhero flicks cuz they suck with Superheros movies; Steven Speilberg, Ridley Scott and Cameron would be great but they are too good and wouldn't do it, Favreau is probably gonna be doing all the Iron Man sequels.
I think these guys are studio favorites, if not a new flashy director:
Roberto Rodriguez (Spy Kids trilogy and Sin City)
Alex Proyas (of Dark City and I Robot fame)
Stephen Summers (Van Helsing and Mummy flicks)
Joe Johnson (Jurrasic Park 3, Jumanji)
Lee Tamahori (Die Another Day)
Martin Campbell (Casino Royal, Goldeneye, Zorros)