That's why i said it was an assumption... But we're talking about replacing the entire science team that ran this place, and researched this technology, with robots that did little more than maintain or interact with experiements. If the robots really did improve the chambers then why were they in such disarray in the first place (the place was falling apart from the start, not to mention walls left open in later test chambers), and how did it continue to decay so badly afterwards. Yet also see all this improved technology at the same time.
This is obviously something we can only speculate about, and personally I believe your worries will be placated. We already have robots who are apparently going to be used for test subjects. There's also the personality cores that are scattered around after being awakened at the end of Portal 1. They seem to control separate areas, and because of their separate personalities their areas might reflect their unique, fabricated selves.
Personally, I believe the area where Glados tested you was blocked off entirely from the rest of the facility in every way. It was meant to be just you, her, and some innocent sentries. In Portal 2 it seems we are exiting that area and venturing into places more open and traveled upon by others. If this is the case, it is neither surprising nor disappointing that they look somewhat different.
Of course, if this isn't the case and things are changed with little regard other than "just because," then it might be a little disappointing, but if the gameplay, humour, and general logic is there, it won't bother me too much.