Engaging with these hypotheticals is a waste of time. It's like spending all day worrying about an extraterrestrial invasion or a meteor wiping out civilization. That's just not the world we live in today, and though it is a possibility it is so remote at the moment that it's not worth investing any effort into planning for the eventuality. We will deal with that situation if and when it happens but for now we should be focused on understanding the world as it is now, and acting according to the objective realities of the present and foreseeable future, not according to some fantasy scenario we imagine in our heads or some far distant future that may or may not happen.

Russia and China at the moment are not imperialist and the geopolitical conditions currently are such that there is no realistic path to them becoming imperialist in the short to medium term. Refusing to critically support them because they might as some point in the very distant future or in some unrealistic, contrived scenario become so is liberal idealism.