Still in the works but sounds like UA will have a subfleet of MAX10s (first delivery scheduled for 4Q20) for premium transcon service.
https://www.flightglobal.com/news/articles/united-plans-lie-flat-premium-product-on-737-max-10s-451309/

763:
N667UA exited MCO maint 2741/15Jan
N668UA entered MCO maint2736/16Jan
N685UA (ex-N590HA) sked to exit GYR, entered VCV paint 2708/17Jan
N686UA (ex-N592UA sked to exit VCV paint, enter GYR storage 2709/17Jan

772:
N213UA sked to exit HKG maint 2774/18Jan
N768UA exited HKG maint 2771/16Jan
N78013 sked to enter HKG 2761/16Jan, unknown work

I think the 781 will be in the rotation for the long-term. The fact that they are in the schedule for the summer suggests that there is some strategic purpose for putting that product in the premium TCON market when WB demand peaks.

My guess is we might see the oldest of the 76C (B/E Diamond 763) in the domestic network until they are removed from service. 7 frames aren't getting Polaris mods (76L) due to age, and they might help to bridge the drawdown of the 75K fleet as they reach "terminal" heavy checks and deliveries of (rumored) premium-heavy 737MAX10s. The 76C is similar in premium capacity to the 75K (28J vs. 30J) and adds about 70 Y seats with the same cabin products. Aside from the 757s, the 76C should be the last non-Polaris aircraft in the longhaul fleet, so it would make sense for UA to deploy them elsewhere, especially given the additional WB frames coming on property over the next two years.

This seems reasonable, especially as the 75Ks like to sell out in the back.

Very nice orders. Surely, they loves 77W aircraft. Is that 20 or 22 77W in the fleet?

Whether if they orders 737-MAX9 or MAX10. That will freeing up the 757 aircraft.

With all those 77W orders, what is UAs take on the 77X?

Possible. They will considering the 77X sometime in near the future. I think UA will kept 77W for a long time. Those passengers loves the 77W aircraft. They liked it very much.

UAX Update
 

Entire post of bad news....
:td:

We seem to have reached the end of 50-seater induction, as least, as only 9 are to be added in 2019. That doesn't take into account transfers, or swaps of 145s for CR2, as it is just a net figure.

Why does UA seem to prefer the CR2? I thought E145 had slightly better fuel economy, but I suppose total operating cost per seat mile could be higher.

We were just informed of an aircraft change for my flight home from Taipei tomorrow on UA872. We now have N2140U. This note is to confirm that the info on the "Polaris Update" page is correct - my new seat map is showing a Premium Plus section.

And more important (if you happen to be me!), they reassigned my seat to 21B, i.e. Premium Plus aisle seat at no extra cost. I'm starting to like sittin' in the Big Chair. :)

Nice treat if you're not one of four potentially downgraded from J.