I could see it becoming the future. But only under a couple of scenarios.

Scenario A: It becomes (strictly) better and/or easier than the alternative. Kinda like how systemd effectively replaced SysVinit within a couple of years, simply because it was a more sane alternative. But this is reliant on the read-only aspect being put in place without affecting existing workflows on traditional distros. So, as Fedora Atomic is the atomic distro I’m most familiar with, I’ll provide explicit examples from it:

• Installing packages shouldn’t take a reboot to take effect. I can see sysexts being leveraged for this eventually.
• Any commands that involve dnf should (somehow) continue to function. It could even be an alias (or something) that invokes something else entirely. I don’t even think most users will care for what exactly happens in the background, as long as the functional expectation is being met.
• The previous two points shouldn’t come at a (significant) speed loss.

Scenario B: It’s enforced on us by (some of) our Linux overlords and/or expected by (parts of) the Desktop Linux stack. Kinda like how the GNOME desktop environment currently has dependencies that are systemd-components. Thus, requiring some hacking to make it work in its absence. Currently, I can only see some RHEL(-adjacent) projects committing to this.

But I think both of the above scenarios are at least 5 years away. While atomic/immutable distros enjoy a healthy (perhaps even generous) amount of development, AFAIK none of them are actually 100% feature-complete^[To be clear, it’s probably at like 95% or so.] compared to their traditional counterparts. So, fixing (most of) the remaining edge cases to make migration possible for every enthusiast that even considers switching, should probably be their priority.