I'm sure Tate will get offered more money to leave than to stay, because he is a very good back. Whether or not he accepts what the Texans offer him because he wants to stay (or if the outside offer isn't that much bigger), is two years away and a lot can happen between now and then. It's to soon to speculate, but my gut feeling is there will be teams willing to pony up and give him the bucks to leave. But maybe Tate will deciede to stay with the two time Super Bowl winning Texans instead.
We've still got this season and next to enjoy him.