I personally doubt it will be worth the effort to support a second compiler in the next few years; it’s more likely that one could replace it with an interpreter under more circumstances (this has already been discussed as a way to reduce startup latency).
I generally don’t find these speculative discussions to be too productive. Proposing huge undertakings (e.g. replacing the compiler) never amounts to much, because you aren’t proposing to do the work yourself, nor to fund it. No one is going to volunteer to take on such a large project because of a mailing-list thread. If anything ever happens, it will be due to someone else’s priorities, not what is written here.