We can expect many things indeed, for Randy Falk (NECA's head) said last year there will be figures from
every movie of the quadrilogy for the 35th birthday.
Now clearly Aliens is the movie they dealt with
the most so far, with many warrior aliens and USCM, the queen, Bishop, and the upcoming Ripley and Power loader.
Then Alien comes next, with the big chap, 2 Ripleys, and 2 of the Nostromo crew in space suit (+ the upcoming big chap in large scale).
As for today, Alien3 has only the Dog Alien, and Resurrection "zippo"
(as Hudson would say).
So I think they are to introduce some figures from these 2 last movies, even if they were not as popular as the former ones.
If you ask me, we're not about to see many USCM coming, I'd die for a smart gunner but it's no secret they had trouble to get the likenesses.
If you think about characters (human or not) out of Alien 3 & 4 that could be worth buying for NECA fans
and eventually deserve to be mass-produced, I bet only on iconic ones : Dillon / Aaron / Jonher / Call, Resurrection warrior and Newborn, and Ripley from these movies perhaps ? I'd personaly like to see more of the Nostromo crew... Lambert (for she's in a spacesuit, so really easy to make) and Ash. The whole team actually... but hey, likenesses, again...
Pure speculation
NECA's first goal was to get Sigourney, they succeeded, but I hope they've not given up on other characters.
And let's keep in mind there might be a Series 6 after that, NECA's Alien figures seem to be one of their best-selling lines
