Ironically, the 747-8 (and probably the A380) are the exception.
The 747-8 is in the process of slowing production from 2/month to 1.5/month, so it would be relatively easy to get it back up to 2. Further, 747-400 peak production was 5/month, so there is a lot of room to grow.
Also makes me wonder even more about that Sky Whale - if the 747 and A380 are already 'too big', why would anyone spend tens of billion$ to develop something that much bigger
