According to Inside Lacrosse, the Toronto Nationals will move to Hamilton, Ontario for he 2011 season, and the MLL will bring back a Rochester franchise. This will be the first time a professional Lacrosse team played in Hamilton since 1998 with the NLL's Ontario Raiders.
The Lacrosse Blog has been one of the top sources for the Rochester MLL franchise updates. It will indeed be the Rochester Rattlers, with commissioner Dave Gross saying Rob Clark of the Rochester Rhinos soccer team wil own them.
UPDATE: The Rattlers will be the former Chicago Machine.