Aside from re-engining the Boeing 737NG with the GE LEAP engine, Boeing has mentioned adding the following features
1. Adding chevrons to the rear of the engine nacelles to reduce the noise footprint, as initially introduced to the B787 Dreamliner and B747-8 jumbo jet.
2. A revised tail cone design similar to the B787 Dreamliner for better aerodynamics.
3. A natural laminar flow nacelle for better aerodynamics.
4. A hybrid laminar flow vertical stabiliser for better aerodynamics.
All of these can be integrated to the 737NG structure. The advantages in doing these are:
1. Unified design and production methods.
2. Premium pricing on the 737NG's that will have these options.
As Boeing will do continuous incremental improvements on the 737NG, we will see convergence between the 2 models as it moves forward.
What I would like to see Boeing do with the 737MAX LEAP are:
1. Slimmer, lighter and more space-efficient seats.
2. Thinner and more space-efficient cabin walls.
3. More space-efficient seating configurations.