In preparation for the construction of the footbridge that links the main terminal to the North Satellite Concourse (NSC) in 2020, there will be a renumbering of some gates effective from 28th March 2019.
According to the press image above, gates 15-22 will be renamed gates 5-12, which should keep the gates in the NSC in consistent order by the time the 200-metre bridge opens next year.
Hong Kong International Airport promises to deploy extra staff, presumably near the “Phase 1” area, to help passengers find their way around in case they get confused. We're not sure how long this extra assistance will last, but given the new numbers in Phase 1 do not conflict with any other numbers elsewhere, I should hope this transition will be smooth enough.
One minor effect of this is Cathay Pacific's The Deck lounge which was previously at Gate 16 will need to have its signage updated for Gate 6, and the Qantas lounge previously Gate 15 will soon be Gate 5.