User blog comment:LEGOfan2010/New Sonic Rumor/@comment-26973802-20131009171545/@comment-26973802-20131011215352

1.) The only other two times you can think Metal Sonic died are in Sonic CD (where he crashes and falls, and Sonic 4 shows how he gets back up) and Sonic Heroes (where he could have been laying dead but future games make clear he was merely knocked out). He's not really like Eggman that way.

2.) The Generations battle can be looked at two ways. Either a.) it's the current Metal Sonic using his shapeshifting powers to take his Classic form for the occasion of  a race at Stardust Speedway with Classic Sonic, or b.) It was Metal Sonic of the past, in which case, ask Iblis and Mephiles the Dark what would have happened to the modern Metal Sonic. Which probably would have been effective as soon as the timeline was restored.

Still, they could pull the whole "his death was reversed by the restoration of the timeline) trick, but unlike Sonic 06, the characters did remember the events of Generations, and Shadow and Silver were at Sonic's party when they weren't at the beginning, not to mention Classic Sonic and Tails before they return