If we speak about regions with russian majority then it's unlikely because despite Russia being very big russian ethnicity culturally is quite uniform. And as for other ethnicities then for most of them it's not economically or politically viable to separate: either their country will become enclaves surrounded by large mass of russian territory or will occupy territory with harsh environment where it would be hard even in the long run to establish sustainable modern economy without tight economical integration with russian territories.

So if we speak about regions with reasonable potential to break away then they are republics in Northern Caucasus and maybe Tyva. And that not very much.