The trend is yet to come. My statement is that, if AMD/Intel doesn't adapt, Amazon has the hardware investment to leave them behind, just like Apple did.
But to be clear on two points: They will probably adapt. And Amazon/etc will probably never leave them behind fully. DCs, especially public cloud, are not all-or-nothing like Apple's Mac Lineup is.
Then the question follows, why would they want something Intel/AMD isn't offering right now? The trend is System-on-Chip. Beyond Security (this isn't the last electrical interference/speculative execution-like attack we'll see). SoCs are easier to service (easier != cheaper. holistic replacement versus per-component debugging. servers are cattle, not pets). Denser. More vertically integrated. Capable of far higher IO performance. Lots of benefits.
Mega-servers with 256 cores and 4 terabytes of memory still have a huge place in all DCs; but not when multiple untrusted workloads are running simultaneously. They're not for EC2/Fargate/Lambda/etc; they're for S3. Highly managed, trusted workloads.
I think it will come down to what you are willing to call 'individual' processors. But actually having physically distinct memory seems like a lot of overhead for attacks that won't matter for 90% of users. Also I would think that the on-board ECC of DDR5 would protect it against these types of attacks.