Nope. It is not a gimmick and will definitely be a "thing" in the foreseeable future. So we have different ideas of the foreseeable future, interesting.
One day it's going to be great. Probably not soon, but one day!
2. Movies aren't often filmed from first person perspective for any length of time.
From my very thorough research (googling "3D movie sick", and looking at the dates; all from the period 2010-2015) this doesn't seem to be a big problem any more. Now this could of course also be because people have just accepted that it is not for them, the people who get sick don't talk about it any more, or people in general have just moved on from 3D, but it does make me wonder. Could the motion sickness not also just be a temporary thing for VR?
I think a game like Myst with puzzles that you manipulate with your hands could be pretty interesting.
I think we'd need to see hard numbers to estimate that (and the hard numbers would need to factor in that this generation of hardware---the Rift and later---is much higher-fidelity and responsive than its predecessors and tends to trigger less nausea).
Wow, that is a very pessimistic approach to a problem. What are you even trying to suggest here, that we have a problem right now in this new tech, and no one will ever, ever ever, solve it because... you think so? People are solving way harder problems out there than this. Like going to Mars for example. I'm pretty sure we will solve motion sickness in VR.