The only way to make these dividends untaxed would be to somehow keep track of dividends separately in your 401k then not tax them when you withdraw the money. I have seen no indication that 401k's were going to be modified have you? No, but funds are ALREADY tracked separately in your account depending on tax status, so the default position is that dividends would simply switch categories.
We'll have to wait and see what actually passes Congress, but the assumption that dividends within 401(k)s will be taxed is clearly premature, and probably wrong.
It is still cutting the tar at the wrong place. Why is dividends better than interest. Banks also pay taxes. Thus interest income is often taxed twice as well. I'm sure there are many other types of double taxitation.
Be honest and cut it at the Corporate level to encourage corporate growth and honesty in the stock market.