Good observations. Buffett's problem is in his long position on the euro. He may have taken a hit on the Yen this past month, but that won't last long. Nor will it get much better, btw.
As for the Yuan, clearly there is only up to go. I think the market has already accounted for this, so when it actually happens there won't be much surprise. The dollar will actually strengthen elsewhere as result. That may be counter-intuitive, but the way it will be. So even if Buffy is long on the Yuan, it does him no good if it strengthens, for it will only help the dollar elsewhere.
The problem currency traders have is with the euro. While smart money has gone to such places as Korea, for example, the politically-biased moves have led to euro illusion. Won't happen.
An interesting point. It would be entertaining in a sad kind of way (for non-holders of B-H shares there might be some offsetting schadenfreude) to see the Sage of Omaha fall into a trap similar to the one that the geniuses at the FHLB in Seattle have sprung on themselves - - -ending up with a portfolio that is hedged in such a way that they lose big whether interest rates rise or fall. (This is not all bad; maybe such pratfalls will encourage Congress to provide some more authoritative adult supervision for these players when it addresses GSE supervisory reform later this year.)