Warren Buffett certainly knows what he's doing, and the fact that he's ditching banks stocks has me thinking that something big is brewing, either in the banking sector in particular or the economy as a whole.
I agree with this, whale investors usually take positions in certain assets after some inside information or some market activity which would be reflected at a later time. Warren Buffett usually is attracted to firms with positive net profit margin and a high asset turnover, he is also attracted to assets which grants dividends to shareholders.
The current financial uncertainty may have influenced his decision to go for stability over speculation.
On whether or not he owns bitcoins, it's possible without it being made public. Berkshire Hathaway has previously requested that some of their holdings not be made public by the SEC, without any public news, there can be no certainty.
He can also of course have a private wallet.