One crucial point when we talk about high core count parts is memory and IO bandwidths. In the end, that'll determine the overall performance of your server. I don't see ARM parts, due to their relatively low single-thread performance, as good for compute-bound workloads, but, with memory and IO channels significantly faster than current x86-based parts, they could be competitive in IO bound ones.

I'd love to see more diversity in the server space, but reality is harsh.