To be honest, Funcom doesn’t even make any claims that there is a tech support for their customers. Any in-game assets we lose are going to be gone, no recovery services.
That said, with the latest vanishing thralls issue, we have seen that Funcom is willing to do complete rollbacks in case of a serious disaster. So, if the update causes massive stability collapses (not just a single niche DLC foundation thing) they’re more likely to revert the update.
Hope for the best, prepare for the worst. Private servers and Single-Players should always backup their game databases before major updates anyway.