Don't you think so? I think it would make sense to call them "Classic 747's" starting beginning of next decade. Now that the 747-800 is coming certainly, Lufthansa just launched the passenger version as discussed in another topic, the 400 will be out of production in 2010. I don't think that after 2012 we will still see any 747-1/2/300/SP in passenger service.
There are now three generations of 747's like there are three generations of 737's.
The 747-1/2/300/SP's should now be called early 747's like the 737-1/200's are called early 737's.
The 747-400's should soon be called Classic 747's like the B737-3/4/500's are called Classic 737's.
The 747-800 is the latest 747 like the 737-6/7/8/900's are the latest 737's. I also think that the 737-800 should be called NG747 like the 737-6/7/8/900 is called NG737. If Boeing ever makes a 747-700, a shortened version, should there be a market for such a variant, it would be mentioned as 74G in the airline schedules.
In the 1980's when the B737-300/400 was brand new, it wasn't called Classic 737 was it? If you called it then Classic 737 at that time, you would have been laughed at. It is not unreasonnable to think that a 747-400 is soon to be a Classic.