Funnily enough I actually have an update on that now
On May 22nd the HK government is requesting a yearly update to Disneyland's performance and early notes say that 4.5 billion of the collective 10.9 billion has been spent up till March 2022
That puts about 5 billion (or 650 million USD) still to be used for only the Quinjet as every other project has now been completed (or in Arendelle’s case functionally completed), there is no current info if this money is earmarked for Quinjet specifically or just park expansion in general, we may get more info on May 22nd.
https://www.legco.gov.hk/yr2022/english/fc/fc/w_q/cedb-cit-e.pdf