United is unlikely to ever divulge such data, at least not in any granularity.

​​​​​​If OP is trying to use the data to gauge overall upgrade probability, even if the elite population is disclosed, still a crap shoot, as there are a lot of actors to consider.

A recent trend: airlines such as United have been mastering the art of upsell. You could be a GS, you could have "Chairman" status, but you may still be sitting in the back.

For example, just flew LAX to SFO, every single GS preboarded sat in economy; 1K preboarders, only 2 people settled in F, plus another pax in F during preboarding was in a pilot uniform.

If you want to sit up front, especially on domestic rights, the common advice here is buy F.