Or both? I'm not familiar with how things have been been done on other language sites. Is it acceptable to cover material for beginning, intermediate, and advanced users alike?
Everyone could commit to the proposal, from experts on the one site, to just curious on the other. There's no reason to close the site also for people who don't know Russian and plan to learn it, or are considering learning it.
As long as the question is about Russian language and its usage, and the author made effort to find answer before asking it (it involves checking existing questions, googling, searching in dictionary etc.) and the question is written in clear and understandable way, it should be allowed.
I think we should support both kinds. The level of both people who learn Russian and those who can answer their questions may be very different.
E.g. I'm not proficient in linguistics at all, so I won't probably be able to take part in discussion about the advanced cases of my native language, but I can answer most of the basic and intermediate questions.