Depends on the kind of Amiga accelerator. If you're talking about one with extra memory and a faster CPU then what's not to like? It does exactly the same as before but faster and with more memory to do stuff. Granted the idea of stuff like the Vampire which adds RTG and IDE too is getting to the point you describe where the original hardware becomes little more than an IO terminal.
I'm mixed on the Vectrex32. It's an incredible device that does some very nice things (the debug, single step, change variables on the fly, all great stuff). It's basically like taking an asteroids PCB and moving all of the game code side of the board to the PIC and the Vectrex carries on being the DVG side in the same way it always has. In fact, the more I think about it, the more it is EXACTLY how Atari did it.
Will it gain mass market appeal? I dunno about that. The price is a bit steep. Don't get me wrong, I can see why and I think it's worth every penny but if you buy one you're going to be left with the prospect of writing games for a system not many people have - I guess only the creator knows the numbers there.
The other problem for me is BASIC - Ugh !! (but that's just me I guess)