Texas won’t have a choice. They will have to accept marriage from other states. Courts will impose it on them, if other states have it.
So far you won’t have to accept “married” turd burglars from Michigan. We said “NO”.
It is an open question as to whether if one state legalizes gay marriage, and there is no federal prohibition, if every other state has to at least recognize gays married in other states.
And don't worry, eventually the supposedly "pro-business" folks will fall over themselves to support gay marriage once the ball gets rolling. Having to deal with employees/customers/business partners in states with different laws with regard to gay marriage will be deemed to be to complicated and bad for business.