As you likely know, ELO has no maximum upper limit and chess has 10^120 possible matches — so in theory maximum ELO for chess has a long way to go, assuming there is even one engine that keeps improving over time to beat its prior version. Huge aspect of performance is tied to availability of compute; as such, my understanding is that if quantum computers ever became mainstream, even a “dumb” algorithm using true quantum computer would beat non-quantum algorithm over significant number of matches and the “ELO race” would then only be define by progress by the non-quantum algorithms against themselves. Basically, at this point, it’s a race that’s already theoretically over; might be wrong though.