Currently questions not containing enough English text are excluded from Hot Network Questions. Some sites, like SO.RU or SO.PT, are manually excluded. It may sound like a good idea, but it's too English-centered and doesn't let non-English sites in the Stack Exchange network receive bonus traffic, which is especially important for growing beta websites.
There's no Languages I understand field in the user profile, but there's a Location field. Based on that field, there're 20,703 users living in Russian-speaking countries. Most likely, most of them don't even know about Stack Overflow in Russian. And they'll never know, because there're no clues on the main Stack Overflow website.
Most likely, there're even more users speaking Russian, but there's no easy way to know. Another solution (or an additional option) is to guess language based on IP address or Accept-Language HTTP header. Ideally, the filter should also be manually configurable, but in majority of cases, a good guess based on this information should be enough.
So, my proposal is: Based on user's location field (or IP, or Accept-Language header, or all of above), include Stack Exchange websites in other languages in the Hot Network Questions.
P.S. One of the reasons I'm worried about Hot Network Questions is that SO.RU faces stiff competition from a Russian website network (Habarahabr and its satellites) which uses its popularity to boost traffic on Toster, another QA site. It would be great to see Stack Exchange network use its power too.