About ascendancies in event .

I have a question about how the Ascendancies will work in the upcoming event. Will they be additional, like in the Affliction league, adding to the existing ones (mega buff), or will they replace the existing ones ?

Because if they're going to replace the existing Ascendancies, it will be a somewhat pointless event, just something done hastily and without much appeal. However, if they are additive to the existing Ascendancies, we'll have the most fun event of all time.

They'll replace existing ones.

People are generally quite interested in it as it allows for crazy interactions, including build combinations that would require legacy gear from Standard or wouldn't be possible otherwise. Also there'll be other stuff than just ascendancies.