You fail to realize that this isn't like 3D printing, or other low volume manufacturing. You can't just setup a 100nm Si lithography lab in your spare room and churn out RISC-V chips.
In 5 years - realistically we will have a few high performance(non-mobile) ARM chips manufactured at economic scale. Any other type of disruption would require Intel and AMD to fail and relinquish the supply side capacity... or China investing billions into new chipmaking facilities now.(it takes a few years to build that capacity)
So I think that we will have a four way competition between Intel, AMD, Apple, and Chinese RISC-V chips.
That being said, I don't see x86 dying, I think AMD and eventually Intel when they wake up will be competitive.
China cannot be competitive at the razor's edge if its semiconductor companies depend on promptly copying/stealing technology that European, Taiwanese, and American companies bring to market.
SMIC has already produced some 7nm chips without EUV.
As for EUV for the further future, there has been quite a bit of research in that domain for many years in pre-emption of this, and while I think they will be a node or a node and a half behind for a while, they will almost certainly have one ready eventually. Of course, that will be accelerated by stealing data on EUV machines, or maybe buying a used EUV machine from someone and reverse-engineering it.
The lithography companies actually have to talk about the measures they take to stop China from stealing their IP on their earnings calls.
China is a manufacturing hub, but its (often government backed) chip companies run low-margin businesses that don't make enough money to invest heavily in R&D. Go look at Apple or Qualcomm's gross margins and compare them to Huawei or Xiaomi.
Most OSes are still pretty well situated to handle this. Java remains, and is easily cross platform. I can run Java-based proprietary games like Minecraft on my POWER9 desktop, despite no-one involved probably ever considering ppc64le a valid target.
The CLR on Windows is also pretty easily cross-platform, although it won't help legacy x86 PE executables. Apple has solved this for ages on the tooling side, encouraging production of "fat" binaries with many arches since OS X was NeXT, and your .app packages needed to run on x86 + m68k + SPARC + PA-RISC.
Emulators like Rosetta (and qemu's usermode emulation) can fill the gap of legacy executables, while these other technologies can make the end-user experience good. Of course, that's only if a) someone writes your platform's equivalent of Rosetta, and b) developers write crossplatform apps.
So, the answer depends on how cynical or optimistic you are :-)