It probably could be beefed up enough to fire 9mm , but it'd be a real kicker - it jumps enough with the .380.
I certainly am not from Ruger, but my family owns 5 LCP's amoung us (and we all love them and carry them) and the reason we bought them was looks / weight / concealability / price (not necessarily in that order).
This little gun is very nice looking compared to it's competition (just my personal opinion) and it crazy how light it is and how easy it is to carry. Making it a 9mm might change all that.
Just my .02 worth.