I think it depends on what we find out about the one piece world, Shanks in my opinion should have a great life after all the trouble he went through, but since the afterlife exists in one piece he would have a way better life in heaven anyway, even if he passes away because of a fight, but he may not pass away because of it,
However, I think BB vs Shanks, BBP vs RHP, Is bound to happen, both because of their own plot and for the effects that this fight would have on us.
Without this, I really don't see how the BBP could be the final (pirate) hurdle their are meant to be. Especially with Kuzan out of the equation.
Not to mention, Teach personally doesn't have the hype to be above "even" Kaido now, let alone Roger.