I'm reminded of one of Safeway's stores near my house. They were doing OK. Then Target came in across the street and started selling a few grocery staples at much lower prices. Target siphoned off just enough foot traffic and business to cause Safeway to close the store. Of course, grocers have much tighter margins than department stores, but that's what Macy's has to worry about with jcp.
After last week's presentation from jcp, I visited a couple of their local stores. jcp needs to do a lot of work on their stores's interiors. One large jcp store had the same brown palette from the 1980s or early 1990s. Their interiors need freshening. But given that the top two execs are from Target and Apple, I'm sure that will happen. Just not in the next few months.
I don't think Macy's and jcp's clientele completely overlap. However, after not too long, jcp will definitely improve to the point where they will take some percentage of Macy's business, at least just enough to hurt.