Looks like there will be less beef in coach, and in UF on flights out of SEA.  Check out this announcement in Onboard Updates (Jan 19):

Effective immediately and due to lower customer demand for beef, we have reduced the ratio of beef entrees in United Economy on flights from North America to the North Pacific and from Japan to North America.

Additionally, on SEA outbound flights in United First, we have removed the roast beef from the deli plate.

We are continuing to monitor the beef situation, and if necessary, will make additional changes to meet customers' entree requests.