I think that future Peter left the scar to remind him of something. His failure to kill Sylar, the fact he blew up NY...something.
I was surprised about Linderman but not DL or any of the others that got capped last night. Ted should have known what was coming and gone nuclear on Sylar, it's not like he couldn't have melted his way out of restraints to defend himself.
With him deak that really only leaves Hiro and Peter that have the ability to kill Sylar. Claire could assist by delivering Mohinders virus to shut him down, maybe, but I don't think she could kill him. I'm guessing that someone is going to explode next week and that's going to be the ending we have to think about for the summer.
And as much as I love this show, that's just going to piss me off.