Yea, there's certainly room. Think about the whole top left of the Showcase, where they have plopped the "Trading Post" or whatever it is they call it...
There are always rumors about new countries, but it comes down to a few factors (from what I hear when asking CMs, at least.)
1. Cost. Countries need to put up the cash in order to get a pavilion, and I certainly do not think that Russia has cash to be throwing around these days, it's not exactly in the best shape these days.
2. It has to be different from the rest of them (to an extent.)
This was the one thing that (So I heard) kind of eliminates Australia -- are the buildings and structures in Australia all that different from England? They started out as an English colony, and certainly many English aspects would be incorporated into their everyday life. Granted, there would be differences, but would there be differences enough to base a pavilion off of it? I am not certain of that, although I certainly am not positive that the opposite is true, either.