I mentioned it in the other thread, but the reason they added the red tape warning to "spend tomes or else" is because the end of the event wasn't tied to the servers going offline for a new patch. The quest would just expire just like all other special events.

5.57 patch is next week, but the only hint they gave during the live letter was they would add echo to certain content. Likely Eden's Promise savage, and probably Diamond weapon NM/EX after XX minutes of wipes. You can hope for a hotfix, and hold onto the tomes since it can't hurt. and we are getting only one more patch, 5.58 before this expansion expires.