Cyanogenmod is just getting a rebrand to Lineage OS. Even if that team completely exploded, whoever is the number two ROM would just get a huge influx of devs as it becomes the new number 1 choice.
Not to endorse piracy, but as for "the community will provide" look at how these sites progress
Look at Piratebay -> KAT -> ExtraTorrent
If there comes a time when ALL major manufactures lock their phones so tight we can't install custom roms, the "community" will surely just kickstart their own open design. Today's phones are so common in form/function that it wouldn't even be hard. A small team of subject matter experts could collaborate on a design then send it to china to be built. As long as Gapps is easy to install, it wouldn't take any effort to sell to the Android elitist community.
Honestly, I'm just surprised there isn't a good one out there already. The Nexus line has probably helped keep that at bay. We'll see how things go with the Pixel brand.