thomas just recently took the time to answer the communities most frequently asked questions. you can real all here: Answering some Frequently Asked Questions!
as a short answer: no, not with every update. they will try to avoid it, but it might or might not be necessary again at some point.
so obviously they cannot promise to never do this again, but i trust it will only happen when unavoidable like with the breach, where whole systems like the enchantments, loot drops etc. get reworked.