As per this article:
https://tftc.io/martys-bent/issue-1170,
If Russians are able to get transactions included in blocks alongside individuals from countries who are still connected to SWIFT, it sort of makes the chord cutting mute. In an attempt to prevent this from happening it is totally possible that the US government and other NATO governments would try to thrust regulations on the mining industry to keep a blacklist of Russian bitcoin addresses at all times and never mine a block with a transaction that is sent from any of those addresses lest they want to be subjected to harsh punishments for violating sanctions. Worse yet, they could even try to force a whitelist of approved addresses tied to the identities of individuals and make it so mining pools are only allowed to interact with those addresses.
Apart from what the others already posted regarding Bitcoin, be aware that it's not like SWIFT is like a complete isolation of the Russian banking sector. At the end of the day SWIFT is still "only" a messaging layer, so while it will make international banking more cumbersome for Russian banks, they can still process transactions by other means long before Bitcoin may come into play.
What's going to be more interesting is whether the Federal Reserve and the European Central Bank are going to cut off Russia's access to its foreign currency reserves. If they block Russian transactions of USD and EUR at the settlement layer -- which they can do since USD and EUR settlements between banks need to go through the Fed and ECB respectively -- that's when Russia's banking sector will start hurting. It will also be a reminder of the riskiness of foreign currency reserves and that having a non-governmental supranational currency in reserve may be more valuable than governments currently assume.