Hypothetically, it could be possible that they pick up some slots for certain markets that their corporate clients demand. Remember that UA used to have all of Disney's business... until they left JFK. So they might pick up slots from AA/DL/AS/B6 for certain key hubs that either have high corporate/premium demand (LAX, SFO) or are in-demand for connections off of partners (ORD, IAD, I guess?). The issue then becomes the high fixed costs associated with operating a station with service 16 hours a day, and premium passengers are interested in expensive lounges, and even which terminal could they get space in (Likely T7, but T1 isn't off the table if DY or another carrier there goes kaput, and in T1 they could use the LH lounge). If it lets them pick up multiple $50M+/year clients, they might do it.
This is asssuming corporate travel picks back up anytime in the near future. And also why would UA be better positioned to pick up these contracts, instead of the current contract holder? Is UA uniquely positioned to come out of this situation financially better than DL or AA (AA, yes, DL probably not)? Even though UA is telling people to expect massive layoffs come October 1st, so they aren't expecting to be in a finacially healthy spot after this.