Cruz has an excellent legal background, arguing cases for conservative causes, several before the Supreme Court. He started his legal career as a clerk for Chief Justice Rehnquist.
My guess is that SCOTUS justice would be Cruz's lifetime dream. Plus, the Senate may wish to confirm him to the SCOTUS only to get rid of what to many of them, in both parties, is an annoyance, if not a menace within.
As to his not being on Trump's "list", remember that the two of them had been bitter rivals in the Republican primary process, and now things seem to be simmering down between them. In fact, Cruz's endorsement of Trump weeks before the election could possibly be considered a play on his part for a SCOTUS seat.
There was never an endorsement. Cruz never mentioned the name, TRUMP. His so-called “endorsement” was a suck up to Pence, in Indiana. Cruz simply made inference when asked about TRUMP. He said “You can see the name on the plane”.
Cruz may sense his azz is ashes in TEXAS and Trump has possibly toyed with offering him a rope with which to hang himself with and get him out of TEXAS.
Not sure that the Supreme Court should be the rope, however.
But, I hold grudges and do not to see or hear anything more from morally challenged Cruz. Recall Carson. Recall fixing delegates everywhere, worst case in Colorado, and filling TRUMP earned delegate slots with his own delegates in sooo many states.