I think it would depend on whether Tywin considered Tyrion to have been broken to his will or not - by learning the harsh lessons and consequences of dallying with whores and, more importantly, in defying your father and family patriarch.
If Tyrion was still defiant, then being able to execute him would be a regrettable, but simple solution. A sacrifice of a piece on in the Game of Thrones.
On the other hand, a compliant Tyrion is an asset - he's smart, capable and he's still a Lannister - heirs and marriage are useful, but not so useful that it's worth have a disobedient child. You can see that in his dealings with Cersei and Jaime - he will tolerate minor disobedience, hate and fear, but not to the point that it harms the Lannister dynasty.
If he considered Tyrion a threat to the family, or of no further use or even if his death has more benefits than otherwise he would have him executed.
It's difficult to tell if Tywin planned to execute him - he's more pragmatic than that, but he certainly would have if he felt it was necessary.