I think we can officially say that Peter Parker will be making a return in the Ultimate universe. In Ultimate Spider-man Fallout, Thor has an inner monologue while he's at Peter's funeral, about Odin is moving the world tree to Earth ("Midgard"
wink and there's a panel where Wolverine, Cyclops, Wasp and Peter are all sitting at a table filled with food just having a good time in Valhalla. The only way to make sense of that, of course, is to presume that after they died their spirits moved onto Valhalla (and they now exist in
Valhalla).
Later, in the same trade, Nick Fury asks Clint Barton for a situation report. His response is:
Hawkeye
All right. Give me E.US.S., Uruguay and the S.E.A.R. on the big board, please. First up is the latest regarding this Asgard situation. I know that you've personally spoken to Thor and he assures you that there is nothing to fear here... But the European Union is so spooked they've reconstituted their Super-Soldier program. And... You're gonna love this... We just found out that Jamie Braddock is leading the team...
So, it's safe to say that, based on the European Unions response to "Valhalla" that Valhalla must be floating in the sky in the middle of the Atlantic Ocean or something, and Peter Parker, Cyclops, Wolverine, etc. are all just chilling up there. All the dead heroes (and perhaps villains) of the Ultimate Universe are just chilling up there, waiting to be utilized for plot-based purposes.
At the end of the trade starring Hawkeye, Nick Fury tells him that Valhalla was attacked by The People, and while Thor is confirmed to be alive, everything else about Valhalla is pretty much still up in the air.
Bottom line, though: Peter Parker will, of course, make a return. Wolverine will, of course, make a return. Cyclops, Wasp and most of the other heroes will probably make a return. Once again, Marvel has found a way to bring the icons back from the dead: Valhalla. Rejoice Ultimate Spider-man fans! Your idol still yet has hope for stardom!