McCain is one of more than a dozen Republicans who are not committed to voting for the bill. His absence gives McConnell the excuse to spend some more time trying to persuade others to vote yes or work out compromises that might gain Dem votes without loosing too many Rep votes. The link below shows who is uncommitted and factors affecting their views.
https://www.washingtonpost.com/graphics/2017/politics/ahca-senate-whip-count/?utm_term=.e8b851dab029
Do you honestly think there is a snowball's chance of that happening?