No it won't. Pressure sensitivity is built into the hardware. 3D Touch is just a feature of that hardware functionality. Unless they get rid of the hardware, which doesn't seem likely since it's used for other things, 3D touch is probably here to stay.

This is highly likely, since most people (off this site) don't seem to use it and one of the newest phones omits it.

I sure hope not. If I were buying a new phone this year, that single feature would get me to pay the extra $250 or whatever to get an XS instead of an XR.