To your first question, yes. But it appears he's wanting to move these to new servers. Although, I think the less hassle for the end-users would be to upgrade an existing 3.6 server to 4.0 (as you mentioned), move the users from 4.0 to 4.0, build up a new 4.0 server (if multiples are needed/wanted) using the SRP of the former 3.6/4.0 that was just taken down.
It sure seems like a backend hassle to do the above, but its a hell of a lot easier than dealing with people who want to complain about recradling.
Although if the luxery does exist that the users have OS4.0 already, then the need to do the above (non-recradling method) will not be required, I don't think. But like you said, if OS and BES have to be upgraded, may as well do it all at once. Expectations will already be set for service interruption.