Will shifting Republican and Democrat populations tend to dilute dominant groups in various states or reinforce them?

That is, are we likely to see, say, red states getting redder through moves in from other states, or will we see more purple states developing as populations shift to offset the dominance of one group or the other in a given state?

And which would be better?

Will any significant number of people even do this?

If you live in a state that is heavily populated by the guys on the other team, do you feel inclined to leave and go where there’s more of “your” people? Or would you rather stay and strengthen the opposition?