He's in jail; he has no access to the hardware the FBI seized (with all his encrypted files on them, and it's hard to unencrypt an encrypted file when you don't have a copy, even if you know the passphrase); and there is no particular reason to move the coins at this time, with Mtgox shattered & the database leaked. It's extremely implausible that it's Ross, now.

It's much more likely it's either Karpeles or a Mtgox insider moving around gains for some reason, or the insider realizes their Mtgox account information is now public and is scrambling to disperse their fortune to less-easily-tracked addresses.