If they had infested Sulaco as a test-bed why would they care to retrieve Ripley after all ;) but I guess it won't be about plot anyway, it will be just like AVP, scripted with 'always-the-same' alien encounters around the ship...
I remember when AVP was about to hit stores, devs promissed that encounters with aliens will be mostly random and the AI will be very advanced, what we got was simple get-behind-me AI and scripted encounters in the very same places everytime ...