It means more people on property, but I'm not sure it means higher capacity in the parks. Historically, I understood the on-site resorts accounted for a smaller portion of parks capacity on any given day; most theme-park guests are off-site.
Also I'm not sure the currently-open resorts are anywhere near full-occupancy -- at least not the cash side. Much of what is currently open is DVC, and WDW may be trying to shift more of that inventory back to DVC by opening more room on the hotel side of the business.