This is going to be Tianmen all over again: kill the chicken to scare the monkey. I remember seeing a photo of military vehicles coming into HK a couple weeks ago. If West did little with Russia you can bet they'd do even less with HK.
Highly unlikely for same reasons that the 2003 protests didn't result in a crack down. The rest of the world (especially business) actually cares about Hong Kong. It'd be economic and political suicide to send in troops.
The government backed down in 2003, which is why this could be different. Unlike 2003 when China was still emerging, China is now legitimate and increasingly assertive superpower. China is now much more hawkish than it had been in the past. This is also a new government.
