If you keep it in the water, not only might you still get ripe tomatoes, but new roots will start to form and you can replant it in a pot.
It might droop for a few days in making the transition from water to potting mix, but it will recover and keep producing. You can even bring it indoors before frost and it will keep going. 8)
Check out Bully's "Red Robin at the Office" thread:
http://www.tomatoville.com/viewtopic...ghlight=office