You mean how many chip cycles he needs, right? How many he's got we all know: maybe 2. Then CMOS scaling is over. (Not that things will completely stop evolving, but they'll surely slow down.)
Yes, but we are just starting 10nm now. Go two more nodes (if I understand correctly that is meant here by cycles) and you are at 5nm.
https://en.wikipedia.org/wiki/5_nanometer
to put that into perspective: "An Australian team announced that they fabricated a single functional transistor out of 7 atoms that measured 4 nm in length."
Maybe we can make our way down to single atom transistors eventually, but who knows how long it will take to make that commercially viable.
Of course, 3d chips look fairly achievable and might eke out a few more cycles, but things will get interesting sometime before that 20 year deadline.
14nm FinFet GPU's are only coming in now, and they'll stay on 14nm for at least 3-4 years. 10nm GPU's will probably come out in 2019-2020, 7nm GPU's will come out in 2025 or so, and 5nm GPU's will come out in 2030, that's already ~15 years and considering that everyone is predicting that we'll have to stick to processes longer as the small we get the more time it takes to actually optimize them for good yields and performance you probably have 3-5 years there too.
So even if we do not adopt any major process changes like switching to graphene, solid state photonics to replace the metal pathways and even optical transistors or w/e else people are cooking up to enable us to continue to improve our integrated circuits he can still be correct about the time frame.
Also regardless of what happens or not he was talking about true VR immersion this means that allot has to change other than just how good and convincing the graphics are this also includes learning to develop VR applications and as VR is a very new media that alone can take 20 years.
I think a lot of VR's biggest hurdles for that time aren't dependent on processing power. Focus and resolution issues will side-step some of it (seriously, our eyes are terrible outside of their central focus region!) because there's simply no need to render everything flawlessly as on a TV. Beyond that, there are going to be all kinds of design hurdles. Right now, we have nausea-inducing roller coaster rides and people running into walls because we can't sync up the (already impressive) visual experience with inner-ear confusion and physical boundaries. Just working out what the most compelling designs are for our current VR tech is the work of years, and that's without doing it on the treadmill of ever-improving tech!