You are correct: the original plan was, indeed, to strip Medicare Advantage in favor of traditional Medicare.
However, GOOD NEWS, as of Monday:
“The insurance industry won a major lobbying victory Monday after the Obama administration backtracked on an earlier plan to cut Medicare Advantage payments to insurers by 2.2 percent in 2014 and instead decided to give them a 3.3 percent increase. . . “
More at : http://www.kaiserhealthnews.org/Daily-Reports/2013/April/02/medicare.aspx and many other places if you want to google or bing it.
Looks like the insurance lobby and us voting old folks are being heard, at least for the moment. Just one battle in an ongoing war, so stay alert.