There were many references early on to the possibility of additional people (non-crew) being on the flight deck for those last few minutes. I've seen nothing in conjunction with the release of the CVR transcripts to confirm or rebut that notion.
Anybody?....
a) many voices have not been recognized
b) the transcripts published are 1 month old. Apparently there is already an updated version - not yet available.
c) define "last few" - I read all 40 pages and there are extra voices all over the place.