When I got the X, I quickly realised that this year was going to be all about the 'Plus' models. I have little to no interest in a larger device so it's going to take a lot to make me want to upgrade my X this year. That said - everyone that wants a plus model will most likely upgrade - not a bad strategy by Apple...lets see if it pays off.
Outside of the larger screen size offerings, I see very little coming to this years new X. Most likely the usual processor and camera upgrades. I personally don't even see RAM being upped. They'll reserve the 4gb RAM bump for the + model. At best there might be Face ID 2.0, to support landscape unlocking / slightly faster. I still think I'll end up waiting for the 2019 models though - it should hopefully offer more to upgrade for.
I hope I'm wrong, I hate thinking we are going back to only the plus models getting the best features/internals again