If the warning would have been really private, you would not know about it. Since you know about it - it was apparently rather a public statement as well. We both don't know about the real backroom deals and what exact words are used there. What are the real red lines that are communicated behind the curtains - most of those statements are just show. Part of the game. I am pretty sure, that Putin would like to remain in power and not radiated. But I would not bet on it. There are rumors he is sick - and sacrifice and suffering is somehow part of the russian mentality.