>> It's been a question in my mind that what's going to be future of Boeing 747? Is Boing going to come up a newer series for the B747? B747-500???
For now, the 747-400 has seen a flourishing of orders in the last year. The 744 backlog was dwindling and it looked as though 2006-2007 might be the last year of production, but 21 gross orders (16 net) will ensure the 744 will be in production through 2008-2009.
Boeing is studying and marketing the 747-Advanced to replace the 747-400. The Adv features a stretch in two portions of the fuselage, not a simple extension of the upper-deck only like the 741/742 --> 743/744. Variants of the newer engines on the 787/A350 and aerodynamic improvements
(no new wing) should bring fuel burn cost to the par of next-generation airplanes. The target specs are to match (or beat) the A380-800 economics in a smaller package.
Here's an illustration, I'm sure Widebodyphotog has his spec. spreadsheet available.
Launch is possible this year, as many customers who could potentially launch the aircraft are planning to conclude fleet procurment in 2005