PEK is currently receiving barely a quarter of the flights it was originally scheduled to receive in recent days. Slots for adhoc operations in the current climate are not an issue.

I also really doubt that the Russians have - between yesterday and today - decided that they are not happy with having given EI clearance to overfly. Russian overflight rights are expensive, and they are missing out on lots of fees on this revenue stream as most airlines that paid such fees no longer have services operating.