There are 17 units to get high J and the 3 ex HA units are part of this group.
N666UA is in HKG for the first unit and STC. It probably was delayed by the government shutdown and may be ready to exit soon.
The first HA unit is also in HKG and some maint work was being done prior to N666UA arrived.
My guess is since Y seats will be removed from the 2 to class to High J conversion, UA would utilized these seats for the Y section of the HA units. If so, it would take two 2 class units into HKG to provide seats for the first HA unit.
These High J units should take less time than the ITPE to Polaris configuration as there may be less maint work - I don't think Y changes much (lavs/closets). All of these aircraft were reconfigured with new Y seats in and around 2012.
It would make sense to enter these High J units into the fleet quickly as it would be a real problem subbing or floating units with a vastly different seating configuration. N660UA should exit Polaris mod within a couple weeks and that will allow 2 or 3 High J mod lines in HKG. Unless maint work is required, if I were deciding I'd rush the reconfiguration and bring the aircraft back next off season for additional work.