First, no one's put forth the premise that all concessions will be at one end of the Dome. Of course that's ridiculous.
Second, check out the south side of the Dome next time you're up there. At its tightest, it's about eight feet from the curbline of a road that SU doesn't control. They're not expanding to the south in any significant way. (And if you got a sense of what's between the back wall of the current boxes and the exterior wall of the building, you'd realize that that's not necessary - there's plenty of room to significantly widen the concourse by using mechanical/bathroom/concession space more efficiently.)