I disagree greatly with those who think that there is nothing to be concerned about yet. I also disagree with those who think that it can't happen. I think it has never been in more danger of happening.
First, Speaker Ryan has an explicit plan for Medicare privatization. See his plan A Better Way. Much of that plan has actually been passed by the House previously. Ryan has said explicitly that he wants to do the Medicare privatization as part of the ACA repeal within the first month of the new Administration. If done as part of ACA repeal, I think it could easily be done without many people even realizing it was happening.
Tom Price is an explicit proponent of Medicare privatization. He will be HHS Secretary. In his capacity as Budget chair he said that Medicare privatization would be done in about 6 months.
For reasons that I won't go into because I don't want to get into political stuff I think it is highly likely that Ryan/Price will try very, very, very hard for Medicare privatization. And, I think it is very likely to pass unless there is a lot of public outcry.
One way Ryan's plan tries to assuage seniors is by allowing those on Medicare and those over 55 to continue with traditional Medicare. That might sound OK on the surface. However, this would mean that traditional Medicare would have ever shrinking numbers as recipients died off and were not replaced by younger Medicare recipients. Even now, the "younger" Medicare recipients need far less care than older ones which holds down Medicare costs.
If traditional Medicare only has a fixed pool of people without new people (those now under 55) coming into it, that will be a huge problem.
It is possible that traditional Medicare would be allowed for those of us over 55 (DH is on Medicare, I am 62) but that there would be a voucher that would initially cover the cost. But, as the traditional Medicare pool got smaller and smaller and costs went up and up (as the age of recipients still in it only went up), then the voucher would no longer cover the cost and recipients could end up with a voucher which covered only a small fraction of the cost of traditional Medicare. The goal there would be to force those people to buy the privatized insurance instead which would have much higher out of pocket costs, would likely be more HMO like with narrow coverage networks.
I don't think that they will get rid of standard Medicare for people my age and those on Medicare already. But, I think many people don't understand how people our age could be harmed by privatizing Medicare even for younger people. And if people don't understand that harm then they may not fight against it.