I noticed that so far there have not been any Adeptus Mechanicus cards for either the Space Marine army or the IG one. Is there a possibility that they will become a faction of their own? This is something I would very much LOVE to see.

I would hope so, if only for the game not being finished with the third warpack-cycle. If there was really AM as new faction, it were 3 Imperials in contrast to all other. I don´t think this would be so interesting, though. I really can´t imagine any other faction either. As for the allies wheel, all factions are already out in the open.