Reasonably, Intel, AMD and Nvidia are all safe because Apple will not take up 100% of the CPU and GPU market. Apple has neither the manufacturing capacity, nor even the will to compete at the lower end of the market. The high-end GPU market is also safe from AppleSilicon, for now.
But AppleSilicon will take some wind out of the sails of x86. And if that example inspires further architectures, possibly with their own OS, computing may get exciting again. Let's roll back to the 90s, when there was Microsft on x86, Apple on 68k and then PowerPC, NeXT on 68k and then x86, Sun on SPARC, SGI on MIPS, BeOS on PowerPC and then x86…