I do not believe there is any way to make a withdrawal from a 401(k) in anything other than cash, nor do I expect that requirement to change.
However, depending on how long you've been working, you may have other sums in your account that are treated as post-tax dollars, and those will receive a different tax treatment (they won't be taxed) when you withdraw them. It's not a big deal to lump any future dividend payments within those accounts into that same "tax-free" status.
I haven't seen the text of the President's speech, but apparently he didn't mention this aspect at all. In any event, these are the kinds of details that would necessarily be addressed in the legislation to be introduced.
Which means, of course, that we here at FR need to start leaning on our Senators and Representatives to get ourselves included in this latest piece of federal largess.