I empathize with your dilemma. A manufacturer changing the way they do business is, naturally, a source of interest and concern to retailers who sell that manufacturer's product, or those who would plan to become such a retailer.
At the same time, I can't help thinking that, y'know, for time immemorial there have been rumors of this comics publisher being sold to that one; of publishers shuttting down; of reducing the number of comics published; of increasing them; etc., etc.. At some point or another, almost every scenario for comics' future has been rumored to be imminent. Sure, some of those rumors have turned out to be true. But plenty of 'em haven't. And while I understand why a business owner would want to be aware and informed about such rumors, at the same time, I can't quite see why a business owner would want to make large sweeping policy decisions based on the prognostications of an anonymous person on an internet rumor column.
All that aside, pragmatically, isn't the worst case scenario you're dealing with here is that Mavel disappears? As unlikely as that may ultimately be, that is the worst that can happen, right? Then, since you're in the planning stages of opening your comics store, isn't the challenge to you to come up with a business plan that could survive Marvel's potential and theoretical disappearance? There are extant comics retailers out there who, while they don't relish the idea that Marvel would vanish, are reasonably confident that they could survive that eventuality. As an intellectual exercise if nothing else, might it not be worthwhile to see if you can devise a plan that would do the same?
"[T]hough goodness without knowledge is weak and feeble, yet knowledge without goodness is dangerous, and that both united form the noblest character, and lay the surest foundation of usefulness to mankind." --John Phillips