Word must have come down that the VP spot would be going to Carson instead of Cruz. IMO a mistake but I guess Trump feels he can get more of the vote by far that way in the main election.
There’s no reason for Trump to decide his VP choice now, let alone have word “come down”. Why would he? There’s no advantage to deciding now. Trump is not he kind of guy to close off options unnecessarily. He won’t make a pick until there is a good reason to do so.
As for Cruz, what’s he going to say? Trump will win? They why donate to Cruz? He has to say Trump won’t win.