The past.
Please do not compare the 777 systems fidelity to our previous products.
The 777-III is meant to be different: great visuals+default systems and a flight model, all for a fraction of our regular airliner price.

The present.
The 777 systems is not a rework/mod of the 747 code. It is your current local 747 code as is plus an extra CS code which provides compatibility with CS 3D models. That's why you see some features of the 747 like 4 engines, 747 naming etc. Well, that's what the Essential functionality paired with default 747 systems simulation is all about.

The future.
We are not going to make any improvements of the default 747 code. So systemwise the 777 is pretty much done.

Third party mods.
Hardcore simmers may enjoy the community free mods for the 777. Some of them are quite advanced. We do not support the mods setup and compatibility issues.

What about a "study level" 777 in the future?
Possibly, but it's going to be a 777 Captain IV, if any.