If I was you I would assume that BS won't happen and do a workaround.
And it may be off topic but I would not plan a trip to the Balkans that included St. Petersburg as a mandatory port either.
We are on Pursuit and this was once a BS cruise. It was changed, eliminating Odessa and Romania, and then changed again shortly prior to sailing to drop Bulgaria.
Such is life in the travel industry. Certainty was never guaranteed.