It is still very difficult to see China *not* reacting like India did with Goa.
1 - Portugal (especially by the XXth Century) is not Britain.
2 - IIRC, Goa also had some religious issues tied into the politics. The British Raj had left many Hindus with a very bitter (and completely justifiable) resentment of Christian missionaries, and Portugal had long used Goa as a base for Catholic proselytism. To Hindu Indians, Goa was not merely a tiny scrap of territory that was rightly theirs, it was also a continuing remnant of what was perceived as the attempt of Europeans to destroy Indian culture and religion. China, while surely resentful over the past defeat that Hong Kong represents, doesn't really have a motivation that volatile to justify retaking Hong Kong by force.
3 - Goa also had substantial native resistance against Portuguese rule. I could be wrong, but I do not believe there was any significant native pressure to reunite HK with China proper.
Overall, if the lease was extended somehow (either when originally negotiated, or later down the line) I see no reason why Britain couldn't keep Hong Kong. China may not like it, but if Britain were prepared to fight over the matter (most likely with American support, especially if this is against a communist China) then I doubt China would go to war over HK, especially considering that they were unwilling to defy the US to retake Taiwan, which is of far greater significance.