Medicare as presently set up only handles a small segment of the market...around 15%:

http://www.kff.org/other/state-indicator/total-population/?currentTimeframe=0&sortModel=%7B%22colId%22:%22Location%22,%22sort%22:%22asc%22%7D

The coverage and costs will not be the same if the entire market is under that one umbrella.  Again, those providers participating in Medicare programs offload their marginalized profits to the private side of the market.

I'm not saying it won't work.  All I'm saying is before we sign on the dotted line, we fully understand the costs, where the money comes from, and how it affects service.  That's all.  Simply saying, "it'll be better" is unsubstantiated because Medicare in this hybrid market is not the same as Medicare in a single payer market.