My understanding is that HK future after 2047 is left unclear under the Sino-British Joint Declaration. Not that it's specified to be annexed to the mainland.

Granted, in practice it's hard to see any other outcome from today's lens. But my observation is that there tends to be a lot of this fact-mangling when it comes to territories PRC likes to claim that suspiciously seems to nearly always coincide with the PRC's interests, and I would prefer public discourse at least has the legal facts straight now and when the time comes.