747 classic is absolutely what CS should make now. One of the most important airplanes of aviation history, has many models too so CS could earn nicely with releasing 747-200 and 200 as base pack, and then 300, 747SP, cargo version and maybe some military models.

Only good 747 classic out there is pretty simplified and not anything really amazing graphically, and although they are working on updated version it is clear that they are not going to make it complete system simulation or anything near that.

So I think there would be good slot for CS.