That ship has sailed.
He has lambasted Cruz as not being eligible to hold office, certainly would not get a VP nom.
Anyway, doubtful Cruz would stand beside a liberal as a running mate... his principles matter to much to him.
I would add that I do not think that Trump’s new pals in DC, who despise Cruz as Trump has stated, would allow Cruz on the ticket. You have to make deals you see, and this is one deal that will never happen.