A spokesperson from 20th Centuary Fox was asked about a fith installment to the Alien franchise last week and he replied:
"There are no plans for a final installmnent as of yet, but there have been a few scripts going around. Most of them are quite similar and the film title would probably be something like Alien Evolution or something like that as they all refer to Ripley evolving as a character"
Lets Hope! ;D
Source?
Fox would never give away the title before it had been announced.
I found it on countingdown.com but no dought its some attention seeker