Interesting question. Thinking very abstractly, I guess that on an async CPU, software could more easily avoid polling, and be totally event driven, so we could get rid of timers/preemptive multitasking/any notion of time, and having no notion of time would make it easy to be tickless.
Of course you probably still want load-balancing between long-lived tasks, not sure how you'd handle that with a fully async system.
Q. would tickless kernels benefit from running on async CPUs?