I'm not worried. They've classed up the rooms a lot and finally gave them a reason to be called "deluxe". I have a tough time believing that the rest of the changes to the lobby and concourse area wouldn't follow the same desire to class up the resort some more. The concourse feels out of place and dated when compared to the new rooms and hallways, so changes were inevitable.
As for the arcade in the concourse, its an ideal location. The biggest concern is noise. The early morning parties they have at Chef Mickey's is already annoying, so I too worry about more noise from young kids and teenagers in an arcade. However, some have said it is being placed where the Fantasia shop is, right? I'm sure with some appropriate remodeling of the shop (which has a roof) and placing doors that close at the entranceways, sound from the arcade itself can be limited to almost zero. As with every big change, memories will be lost, but new ones will form. It can't stay in the 80's, early 90's forever. Its called the "Contemporary" afterall.