It certainly could for many reasons.
As has been stated, it could spawn several clones if it takes off, and I'm thinking it will. Also this could be the one game that all the watchdog groups hounded that turned out to be completely innocent compared to their claims, officially making them all look like fools.
And also, it could show people that you can't judge a game strictly by it's title. It also will show those not in the know that Rockstar can make a good, deep game without pushing the envelope.