Domestic forces have always proven to be much more of a threat than foreign ones. The end result will entirely depend on will of the Belarusian people, and whether or not foreign backers holds off for another day given the Belarusian response to these protests. In the case of a dramatic escalation of the situation, there will likely be foreign military support (for both sides), but no kind of foreign invasion. So how this turns out, if there will be a separation of the country like in Ukraine or not, is quite impossible to say right now, at least in my eyes.