Trailer 2?

 Probably the month before the movie starts.  Fox and Ridley love their viral marketing.

my guess is during the superbowl

In between the first trailer and the release date, so maybe March, mid or late is my guess. 

February or March im thinking 

March would be a good time to release a second trailer, but keep in mind we'll have a bunch of TV spots and international teasers releasing around the second primary trailer. But, given how long they waited to release the first teaser, I think we can expect a long wait for any new ones.

I think March is likely because Fox is releasing Logan.It would make sense if a new trailer was in front of it.

I think March too.... i also think we could get pre-screenings around March 24th-26th

While March makes sense in terms of spacing...I'm going to have to go with Resurgence here and assume that the Superbowl would be the perfect time to make sure the maximum number of people are aware the film is arriving in the near future and that it's going to be a true Alien film.

This of course will probably need to be green band but it's also the perfect opportunity to deliver an extended trailer made up entirely of 2 second teaser clips all strung together against some dramatic music to reel in the majority (and most importantly those who were disappointed with Prometheus.)

I'd go as far as saying it would be foolish not to shoot for a super bowl spot.

So by march 24th we will have the movie figured out since they spoiling shit like flipping burguers.