I disagree.
I think Alien is last because people like guest characters.
Plain and simple.
The 1 character that was most requested out of those 4 was Tri-Borg, though.
Not Tri-Borg himself, but either Cyrax, Sektor, or Smoke.
People were pissed that those 3 never made the original cut for MKX, and now they're getting the 3 cyborgs again, via Tri-Borg.
The order for KP2 Kombat Kasts has nothing to do with which character people want more, as all 4 characters will be released on the same day, March 1st.
Had they released the characters in the order that they're doing the Kombat Kast, then I could see the point, but that's not the case here.
My guess is also 50-50 between the people that want the cyborgs back (Tri-Borg) and Alien, followed by Bo Rai Cho and lastly Leatherface.