Need experts on IRAs and 401(k)s under lower tax rates

I’m looking for financial advisors, retirement experts and academics with tips on how investors might adjust their IRA and 401(k) portfolios now that income tax rates have been reduced. In general, how significant are these rate cuts? Which investors are affected the most? How will the new rates affect the decision to invest in a traditional IRA or 401(k)? Will upfront deductions and tax deferral lose some appeal? Enough to affect the decision on whether to open or continue contributing to a traditional account? How might the rate changes affect the ongoing management of a traditional account? Would it have any impact on the choice of investments?
Most important, how do the rate changes affect the choice between a traditional account versus a Roth? And how would the new rates affect the Roth conversion decision? Should investors who did conversions last year be thinking about re-characterizing and converting again now that the tax bite would be lower. What factors other than rates would affect this decision? What else should I be asking? Requirements: I prefer responses by email containing usable content and quotes, and because I usually get plenty I rarely respond to ones merely offering a source for interview. Please include the source’s contact info, full name, title, firm and location.