According to Norse mythology, the prophecy of The Midgard Serpent is the same as The Serpent from Fear Itself - Thor will kill The Serpent and then himself die. But the origins of the characters is vastly different. It could go either way, honestly. So who knows? Source material!
It isn't confusing! If you follow Joe Quesada on Twitter he explains it all. The artist gets to choose whatever they feel like drawing. Not indications of anything that's going to happen in the storylines, just cool art for an anniversary deal.
https://twitter.com/#!/JoeQuesada/status/98815685370720256 and https://twitter.com/#!/JoeQuesada/status/98815981576663041
So, a couple of months ago, Marvel Exec Editor @TomBrevoort asked me if I'd like to do a promo piece for the 50 Anniversary of the FF.
The rules were simple, do any incarnation of the FF that you want from the 50 year history and design the piece for multiple usage.