The LGA slots are pretty valued, but only can be used on a few UA destinations that are inside the perimeter rule (especially because UA doesn't do focus cities too much) so UA must have some ideas. If it were AA or DL, they would certainly covet these more as they serve many destinations.
Here is the current breakdown of UA nonstop service out of LGA: 15x LGA-ORD, 5x LGA-CLE, 7x LGA-DEN, 8x LGA-IAH, 4x LGA-IAD
Here is the current breakdown of UA nonstop service to its other hubs out of EWR: 10x EWR-ORD, 8x EWR-DEN, 9x EWR-IAH, 8x EWR-LAX, 11x EWR-SFO, 7x EWR-IAD
UA can probably do without the slots that it currently uses on its LGA-CLE nonstop route due to
(a) UA being able to increase capacity on LGA-ORD/DEN/IAH/IAD by upgauging to larger planes,
(b) EWR being close enough to Manhattan to be a viable option for those traveling to NYC on UA,
(c) UA already having plenty of nonstop service to ORD, DEN, and IAH out of both LGA and EWR, and
(d) UA having an FF base in the NYC market who is willing to fly out of its EWR hub.
UA can probably use at least one of the slots that it currently uses on its LGA-CLE nonstop route on its LGA-IAD nonstop route since
(a) IAD currently only operates 4 daily nonstops out of LGA compared on UA whereas the other UA hubs within the LGA perimeter already have more nonstop service to IAD,
(b) there is some O&D traffic to LGA from the western portion of the DC metro area,
(c) there are some passengers connecting to LGA through IAD from domestic destinations that UA serves nonstop from IAD but not from EWR on UA.