This probably was discussed to death at the time, but as Loki says in 998 (
https://www.giantitp.com/comics/oots0998.html):

"Look, if that last rift is opened, there will still be, like, ten to fifteen minutes before You-Know-Who gets out, right?

More than enough time to pull the plug, if we all agree on that course of action today."

Which... they didn't agree on that course of action. The jury's still out pending Dvalin's vote. Seems like there's not a "cash-out in time" option on the table because of the hung vote. We already kinda knew the gods wouldn't swoop in and fix it, but it means that the last gate breaking is on the table because if the gods won't unmake the world due to their rules someone has to find a way to fix it...