They couldn't get a majority before. What makes you think they can get 50 votes going forward?
Furthermore, the states will once again be in charge of medicaid and that means that there will an immediate wrangling over money turned over to the states and the adequacy of that money to cover medicaid as it is now constituted. That will lead to pressure on Congress to cut medicaid (as has been planned).
Bottom line, by the repeal of Obamacare without a replacement plan, Congress will have lit a bomb that, when it goes off, will p!ss off a lot of voters and this will create an immediate desire for them to find a solution to the collapsing insurance market.
All this said, it is possible that, if the state boundaries on the selling of insurance are eliminated at the same time Obamacare is repealed, the free market may actually save the day.
I am sure I have overlooked many details, but this is my quick response.