Alright, we won!
The new landlord contacted us a couple of days ago and agreed to let us stay until mid August just like we demanded.
What helped us: staying amicable, communicative and research on our rights.
Thank you to all who participated in this thread!
My SWMBO & I own our flat - so this doesn't arise for us; but I recall reading - loooong ago - that one aggrieved tenant placed the shells of cooked up (& eaten) prawn shells in the hollow curtain rails & in other hiding places around the forcefully vacated flat, and the NEXT tenant and the Landlord battled to find the source of the ever-pervading stench for weeks.
Since you still hold the tenants' security deposit (and unlikely in an escrow account in HK), even if they don't pay within the 21 day as you demanded, can't you just deduct however much your tenants owe you from the deposit and return the rest when they leave? So technically, wouldn't the debt is secured by the deposit, how can you file a bankruptcy petition if that's the case?
CLIC - Landlord & Tenant
According to a judgment made by the Privy Council (the final appellant court for Hong Kong before 1 July 1997) in 1986, the covenant made by a landlord to return the deposit to a tenant is a personal promise, and is thus enforceable only against the landlord personally but not against the new owner. Therefore, unless there are some other arrangements or agreements, the new landlord is not liable to the tenant in respect of the deposit paid to the old landlord.