Does this mean Linux phones might finally be on the horizon? I know Pine64 has existed for a couple of years, but the software is still not in a useable state.
I feel like this would be a lot more viable today than it was when Ubuntu and Firefox tried it. Progressive Web Apps have come a long way, both in terms of quantity and quality. Newer desktop Linux apps have more flexible designs as well, so they could probably be adapted more easily than back then.
How would this change anything Linux Phones? Debian has had support for ARM CPUs for quite awhile, which is what nearly all of today's smartphones run. So how does RISC-V support change anything now?
In the long run, yeah. I wouldn't say they're on the horizon, even when major distros do support RISC-V there will still be serious issues and I doubt most programs will work. I'd wager about 4 years until risc-v is usable for average use.