The Flash Season 1 Episode 23: "Fast Enough"

Would Eddie come back as a villain though? He was a good guy during the whole season, and that sacrifice at the end of the season was done willingly. It would take a whole character rewrite to make him believably evil. I'd like to see him back, but I don't think I want to see him evil.

 

That's not going to happen. When Eddie killed himself he killed Eobard and thus destroyed that time line. That was the reason for the big black hole opening up above the city.

That time line will be erased in favor of a new time line. Some things will be the same other things will be different. However in the new time line Eddie will be alive. Sense Eobard was never born he never traveled back to the past and thus starting off the chain events in Season 1 of the Flash. This also means that Eobard is still alive which means we will get to see him return at some point.