Well heres what I think:
Starscream, Barricade & Scorponok are definetly alive & well (with Scorponok being the acception to this in regards to damage).
Notice the parallels to the Energon Series, where Scorponok is found damaged & offline...
The others who died, Megatron, Blackout, Brawl & Bonecrusher were dumped into the sea.
Cast your mind back to G1 series, on Earth the Decepitcons base is under the sea...
Prime recovered the All Spark fragment from Megatrons chest, this will be the key to Megs & others resurrection.
All the right plot lines are in place for TF2.
Heres how it'll go in my mind...
Starscream take the lead once again, he recalls all Decepticons to retreat to their sea base, he also calls for the recovery of all the Decepticons dumped into the sea...
Starscream calls for re-inforcements from Cybertron, and also ralles all the Newly formed Decepticons on Earth from the Energon wave that went out during the film, other Autobots were formed to but that wasn't shown.
Jetfire, Blurr, Ultra Magnus, Redalert & others arrives on Earth, as does Tidalwave, Soundwave, Sideways, Shockblast & others.
Starscream orders the recovery of the Allspark fragment to recover his lost comrades, he secretly plans to leave Megs at the bottom of the sea, this plan fails as Unicron makes his presents felt and revives Megatron now Galvatron, Blackout, Brawl & Bonecrusher are all given new forms, Starscream is then destroyed by Galvatron for his failings, Galvatron now sets out to recover the Allspark fragment and destroy the Autobots once and for all.
Jazz is revived with the help of the Allspark fragment and the help of Ratchet & Redalert, although Jazz is now quite different from his last form...
I could do this all day....
You could say the dinobots arrive in protoform but crash into a museum and take on their preferred Alt modes, now that would be a sight.
Spielberg wouldn't have any problems getting some dino action in there

Lots of action ensues, and this time round Optimus is killed by Galvatron, the Decepticons then retreats back to Cybertron...
With Optimus down and Ultra Magnus in control of the matrix the scene is set for TF3 which will be set on Cybertron, Woooot, and Prime will make his return to fight off Galvatron & Unicron....