Don't mix bits with bytes.
The Panny 60p mode is 28Mbps (bits per second), which is 3.5 MB/s (bytes per second).
Class 10 cards can write at the least 10 MB/s (I think the Extreme series from Sandisk can do 30 MB/s), which is almost three times what you need to do 28Mbps.
In other words, a class 6 will do just fine here. Even a good class 4 should be able to, though I personally wouldn't chance it.
Note that some DSLRs have been recording H.264 video at 40Mbps for over a year now, and some hybrid P&S cameras (like one of the Canon's) have been recording 40Mbps MJPEG 720p for over 4 years, so 28Mbps in terms of bandwidth isn't ground breaking per say.
BTW, the HD video SD cards are just a gimmick. Just get yourself a good standard class 6.