I just called my guy in Germany and he says production has "not" seized so you are indeed correct in stating the US can still get E39's well into 2003.
Since I was on the phone and I already asked the group if there was any further news on the new M5, my guy says the new M5 won't be represented in the Frankfurt motorshow however it will become available mid 2004 for sure.
Over the next few months there will be spy shots of the new M5 speeding on BMW's racetracks (test runs) I'm told if the new M5 doesn't kill the Mercedes by at least a further 50Bhp everyone in M division will resign.
So get ready for 550Bhp !!!!
Not sure about you gents in the US but I placed a 5000Euro deposit just to get my name on the list for the new M5.