In the end, futureproof is just a term that is used to show how long does a certain part will last, performance-wise (how long will it last depends on the actual usage, age, maintenance stuff, etc)
In the practice, getting a high end rig is just extending the possibility of playing at higher settings longer than the weaker rig (and fulfilling the requirement of future upcoming games)
The sure answer: only God knows
we can only predict and prepare
Or just forget all about this and enjoy whatever u bought (happy-go-lucky solution
)