Looks good for the future of Methane Hydrate, of which undersea deposits could provide 6 centuries of power for our planet. Methane Hydrate is natural gas in a frozen water matrix.
Interesting idea. But its cold down there; take a lot of warming to have that problem?
Theoretically, meteor strikes may have exposed/breached a deposit sometime in history. So large releases probably happen from time to time. How would we know? What trace would these catastrophic methane releases leave in the geologic record?