Removing primal weapons would be a silly idea.

They are adding in all primals they can (as said by Yoshida) - and they have primal items for the new primals. They would be stupid to create an inconsistency in primal gear if the primals that are changing from 1.0 to 2.0 are going to make any appearance (which we know they are - both in instance and non instance).

Just because an achievement is changing is awkward assumption that weapons will go too.

that being said its not impossible the weapons dont come back, though as I said before the inconsistency created would be a bad idea to make.