eXmortis45: Portal was fun but realease ep3 already goddamnit.
In my opinion, with the end of Ep2, the borealis, Aperture Science tie-in they didn't exactly know where they were heading with this. It's clear if Ep3 were ever to come out Aperture Science would play a great role in it... but that whole lore isn't fleshed out yet.
I think it's only logical for Valve to expand on that part of the Half-life universe before doing any hasty moves with the Half-Life franchise. Hey, we may even get some more information in Portal 2 about the Half-Life games and events. (since it's supposedly taking place one century after Portal)
Knowing what they're going to do with Aperture will only result in a better next Half-Life installment, be it Ep3 or anything they're going to call it.