I feel it would have ultimately been detrimental.
The main issue with the PS3 was not a lack of power, but how byzantine the architecture was to develop for, and a more powerful model would not have helped things.
An easier to develop for model might have helped, but that's still asking developers to program an "easy PS3" and "bastard hard PS3" version of any given game, which is just unrealistic. After all development costs for the cell were already high enough before asking devs to put in extra work on top.
The reason why the PS4 Pro gets supported is the easier x86.
Hence why I would think a Pro would mostly just be a stronger GPU (so the Cell could be more used like a normal CPU instead of having also to do all those GPU tasks, simplifying and streamlining greatly the programmation of games), and bigger RAM and VRAM. The problem with this approach would be that the base PS3 Pro would practically have to be a different port of any given PS3 game.
Also, PS4 and XBO would probably not have come out before 2015 if there would have been some mid-gen upgrade for them.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454