It's exceedingly unlikely to happen (and Beijing would likely find a way to prevent it from happening) in the legislature ("Legco"). This is due to combination of proportional representation in the geographic constituencies, and the fact that half the seats are taken up by functional constituencies which are mostly pro-Beijing. And the Chief Executive is explicitly chosen from a pool of pro-Beijing candidates, so that wouldn't happen unless the law is changed. (The law that enacted this in 2014 was one of the sparks for the so-called "Umbrella Revolution")

Some relevant wiki articles:

https://en.wikipedia.org/wiki/2014_NPCSC_Decision_on_Hong_Ko...

https://en.wikipedia.org/wiki/Legislative_Council_of_Hong_Ko...