That's exactly what Trump is advocating.
Trump's tweet said:
"If Republican Senators are unable to pass what they are working on now, they should immediately REPEAL, and then REPLACE at a later date!"
There was a qualifier. He didn't say that they should scrap the bill and just repeal now, he said "If Republicans Senators are unable to pass what they are working on now". It makes a big difference, at least the way I take the statement because it could be taken as a threat to the Senate to get it done or else. He knows that the Repubs don't want total repeal and I do not believe that Trump does either. I think they both want their own version of a healthcare bill. Wish he would have said just "Repeal" and left the "If" out of it. I think just repealing it would be the Repubs worst nightmare.