It was being speculated just a few months ago that Putin is thinking about it/being encouraged to use them. He must be seen to win at all costs, and not-winning is therefore seen as a threat to russian statehood.

E.g.

https://inews.co.uk/news/world/cornered-putin-under-pressure...

https://www.newsweek.com/putin-tactical-nukes-radioactive-ba...

https://www.reuters.com/world/europe/russian-hawks-urge-puti...

I'd put it at 10-15% chance easy.