Hmm, strange but that didn't work for me couple of months ago, and I had to install clean win8, upgrade it to 8.1, then upgrade it to 10 and then just do a clean install of win10... well, I guess something went wrong lol.
Because if its not dx12 only, I can play them on my win8 without any problems. In another words, not worth the hassle. Moreso, since the fabled "performance boost" is a single-digit fps increase, which would be instantly lost in world of awfully optimised at release games.
Why wait for 5+ years? Lol because in 5 years you could be playing full VR games, or we could have sudden revolutional tech discovery in hardware, or the earth could die in a fire, or pretty much anything. I don't find win10 worth the hassle of upgrading/clean installing right now, even with it being free. Although, if I had to install an OS on a new PC, that'd be win10 though - that's what I always do, install latest OS on a new PC; but upgrading is a completely other story.