I think some of bosses will be:
A Queen (OBVIOUSLY!)
Maybe a Space Jockey Xenomorph
A Space Jockey
AND...
A Weyland Yutani Mercenary Commander
Now I know what your saying, Weyland Yutani? Remember, they want the Aliens, plus, they probably found out about this new team of Marines going to investigate the loss of the Sulaco. Now what would the soldiers look like? First, the WY troops would probably be hired mercaneries, armed with all the high tech WY equipment, and they would probably wear the same armour as in the Weyland Yutani soldiers in Alien 3.