How about the -500: an upper deck stretch by 3 meters, plus a forward fuselage stretch of 1.5 meter, which keeps CG unchanged. It’s of course only a matter of 50 passengers…

Good insight there, airlines will soon want a replacement for the 747’s built before 1993 or so.
Another thing… The 747’s current upper deck has six abreast seating (737 style). That isn’t very efficient isn’t it, to stretch it all the way backwards! That would make a widebody-like lower deck, and a a 737 like upper deck. This will create a capacity between the current 747-400 and the A380. That’s great!
On the other hand, stretching the upper deck would disturb the CG. A fuselage length change will have to be done anyway.

We all know that Boeing has been re-designing existing airframes for a long time. For example the 717, and the 737. The 747 is also becoming an “older” design. Do you think this is good to recycle older designs? I think Boding made a good step designing something totally new (7E7), because the last time they did that was with the 757 and 767.
Apparently, redesigning the frames works, since the 737 is very competitive to the A320 and A319.
The 747 has been changed so much over the years with the use of composites replacing the bare metal partially. But stretching the 747, wouldn’t that bring a lot of problems.
-The aircraft will need a new wing to lift the increased weight.
-In order to increase the range, the aircraft will need new, more powerful engines (maybe four of the 7E7’s engines?)
-Maybe the weight would get a bit too high now for the current landing gear. The A380 has four wheels more than the 747 (2 sets are 777/TU154 like). The 747ER aircraft already have a slightly different landing gear than the basic series; but that doesn’t decrease the pressure on the ground.

Oh yes, very good, will become the best house livery after Embraer’s Or DeHavilland Canada’s. Airbus’ livery is boring, but straight.

I think you are right because the gearbox is on the below left and right of the engine, typical for a 737 engine. But isn’t the central “spiral” a bit too big for a CFM56?
Might be just a detail, but CFM56/3 engines have different spirals.

I think it looks like an engine of a Classic 747, but if you think it is taken from a BA aircraft, then it should be a Rolls Royce RB211. But this engine doesn’t look like a Rolls Royce.
It is not obvious how big the engine is. A normal man can stand straight in a 747 engine with plenty of headroom left. How big is it?