My guess is that if Amtrak is "privatized," it will be eliminated entirely within a few years, maybe a few months of "privatization." The NEC might continue to exist assuming there's enough local governmental or non-governmental support for it, but everything else, including HSR proposals, corridor services in California, the Pacific Northwest, and elsewhere, will be ended. Remember that Mexico "privatized" its rail system in the late '90s, and all but eliminated passenger rail services thereafter, with no (AFAIK) serious consequences to its overall transportation infrastructure.