They might consider it after Ridley is done, but the Halloween retcon was much more acceptable among the fanbase than an Alien one could ever be.
The Alien series can go into many directions, there is a lot of space for ideas, it can work with new characters, we can always have new aliens pooping out of somewhere. While Halloween is dependable on Michael Myers, so at this point the only options were either a retcon or another remake, and considering how those failed, retcon it is.