Help with running Episode 14: Tower of Salt

[Havard]

I am right now running (play by post viewtopic.php?p=36056#p36056) Tower of Salt and there are strong chances that, during the various trials in the Tower of Salt, there will be a total party kill.
The trials in the Tower of Salt can be very tough and the text of the adventure itself provides you a way to bring back to life some characters that died in the dimension where the trials are run. However, the adventure doesn't say what you shall do if all characters die and the trials are not all completed.
This adventure is part of a campaign, so if this adventure is a failure and a TPK (including Sulla?), then follow up adventures of the Saga of Hadeen may not become available to play (especially if Sulla dies as well).
What do you think is the right solution?

How about having them captured instead of killed? Then you could run a follow-up adventure where they can escape. Or you can have them be freed as part of a hostage exchange.

Alternately, have the PCs be killed, but Sulla is now captured so the new group first has to rescue Sulla before continuing the story?

-Havard