Seems like yes-ish for check-in, no-ish for security. T4 and T5 still won't be connected behind security (construction on the connector hasn't started), so it'll still be easier for folks going to T5 to go through security there, but presumably the wall will go down between the T4.5 core and the new T4 (so one will be able to walk from T5 check-in to T4 check-in fully indoors).

A bunch of space in all the new T4/T4.5 construction is going to remain inaccessible until construction is (close to) completion, there was a LAWA board report about it a few months back. It is/will be in use as swing space for displaced back-of-house spaces.