Yes, it appears that the flathub maintainers have published Sublime Text under flathub. This is not an official distribution channel by us, and looking at the spec (https://github.com/flathub/com.sublimetext.three/blob/master...) it seems to rather automatically install Package Control, but also in a rather brittle way. Sigh.
If many distros and people want to use a flatpak to install software even with these drawbacks that would be a good indication that it would be worth doing upstream.
I try to respect a self-imposed policy of not installing proprietary software that's not properly sandboxed, as I have little control over it (think about the Remote Code Execution hive that Steam games must be).
I do not use Sublime Text personally, but if I ever want to try it, I'd do it trough a flatpak. Yes, sandboxing permissions might not be perfect yet, but a little sandboxing is always better than none...
It will be interesting to see if Flatpak, Snap or AppImage ends up being the predominant force in the new wave of Linux packaging. Knowing Linux, users will probably expect projects to support all three. :-)