Its far from automatic. In any case, all they'd have to do is send a polite letter to the little store granting them the perpetual right to be similar in the way that the currently are. As SJ said, "not that big a deal".

Compared to patents, trademarks do not really generate that much abuse of the law. On top of that everybody seems to agree that their benefits (i.e. prevent businesses from confusing consumers) totally outweigh downsides, which is not the case with patents. The rare cases of abuse actually generate quite a lot of bad publicity.