We've got four dimensions. Why not more? Makes perfect sense. Worth investigating, especially when physicists agree.
In M theory all the extra dimensions are supposed to curled up ("compactified") and inaccessible except on beyond-microscopic scales. The strings themselves can vibrate in all those dimensions, but anything much larger than becomes too big to take advantage. So it's not like the other 7 dimensions are out there and we just need technology that lets us see them, but then once that's done we'll be able to move left/right, up/down and/or brill/tove. Some day (deep into the distant future) perhaps someone will figure out a way to uncurl one of the compactified spatial dimensions, but that's way beyond where we are now technologically.
I'm a total layman when it comes to this field, so I'm sorry if my question seems a bit silly. Are there any hypotheses as to what would you happen if you were to uncurl one of those compact spatial dimensions?
To the best of my knowledge, no. To the best of my knowledge though, the first reference to uncurling one of the compactified dimensions was in my post above...so I sure someone somewhere has probably thought about the issue in much greater detail than I have.