Trump is about state rights and has said time and again that the Federal government should stay out of the abortion issue. Pretending he wants to rule one way or another federally about abortion is idiotic.
The problem is that Trump can say what is convenient during the campaign and do what is convenient during the presidency. It would not be the first time that he changes the discourse. That is one of the problems of being so unstable.
But in the end what matters is the electoral support. He will chose whatever delivers his goals and if a sufficient number of Republicans are in favour of a national ban he will have no issue exchanging that for some other crazy legislation of his choice.