It doesn't really matter how many Mir cards are—they're just a home-grown Russian brand of a card.
The real issue is that all transactions inside Russia using Visa, MC or Mir are processed inside Russia by the same entity that runs Mir brand, and therefore won't stop working.
The real issue is that all transactions inside Russia using Visa, MC or Mir are processed inside Russia by the same entity that runs Mir brand, and therefore won't stop working.