Romney and Kasich are biding their time. I wouldn’t be surprised to see an endorsement of Bloomburg if he succeeds in buying the primary, but I’m not sold that he’ll succeed because all the energy on the left is with the socialists, and Bloomburg is only renting mercenaries who want to pay their bills for a few months. I think it makes more sense for Romney et al to bolt in 2021- 2022 and form the milquetoast centrist party nobody asked for. Bloomburg can even bankroll them as the elder statesman.
Just like the Bushes and their ilk bided their time until Reagan was out of office.