Hi.
Not quite, the 'standard' V2 gearbox first used by Tokyo Marui is still very popular and used by G&P, G&G, VFC, Classic Army and others. Tokyo Marui's newest M4 family and Scars use their 'next gen V2' which work slightly differently to the original V2.
M4's that use V2 boxes are mostly interchangeable, although there are differences in features that can be lost when swapping. For example, some VFC gearboxes have an extra external screw and a hole for their bolt release, some G&G gearboxes have bits on the top for their pneumatic blowback. So, if you stuck an standard box in either of those two, it would work but you'd lose those specific features.
ICS use split gearboxes in their M4's, most of the internals are standard ver.2 parts, however a standard gearbox won't work in an ICS receiver.
WE's Katana system use a split gearbox in their M4's as well and have less standard compatibilty than ICS.
Systema M4 PTW's use a split gearbox and their own parts altogether.
That's what I can think of right now, there are probably others I've missed.
Is there a specific combination you wanted to know about?