Optical upgrades?!?! The old 55-250 is already a pretty solid piece of work optically. I can't wait to see how it could improve. I mean, if it gets much better, it would practically eliminate the need to go to an L in that range.
I wouldn't go quite that far: http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=456&Camera=474&Sample=0&FLI=0&API=0&LensComp=738&CameraComp=0&FLIComp=0&APIComp=0
Yeah, the L lens is five times as much, but it is in a whole different league optically.
Not really, if you compare them both on an APS-C body then the L lens is just barely better than the 55-250. On the other hand compare the 55-250 vs the 70-200 is ii at 200mm both on crop and you'll see a world of difference.