Everything I have read has said no changes to backdoor Roths.
I think Roth 401K all the way, even for over 50. Unless you really need the tax break, why not pay the taxes now and never pay tax on that account again? Make it the last thing you ever cash out, because that account growing tax free for decades is a gold mine.
I've had people show me the numbers and the arguments of why it's not worth it (or the same), but nothing trumps tax free growth. The big money is not is the tax break of 5-7K/yr you get right now, but the tax break of hundreds of thousands you get after decades. And I'd make it my most aggressive account.