Umberto, did you realise SimConnect is not necessary for P3D v4?
Of course is still is, that's why is already installed by default. But on a clean install of the sim, the only Simconnect that is installed, is the P3D4 version.
The simulator comes with some sort of internal connection mechanism that encompasses all needed functionalities.
If you mean the PDK, then yes, we use it of course (and not many other developers do), but there are some things that are still not possible with the PDK only and still require Simconnect.
My setup is a proof of this, because it has not a single SimConnect installation and still EVERY addon (and I have loads of them) work just fine. Maybe you should revisit the need of including an external SimConnect installation, at least P3D v4 wise.
It seems it's probably not very clear to you how Simconnect works.
It's a client-server system, with a server part that works inside the simulator, and a client part which works in the add-ons. Of course you DO have a Simconnect installed in your system, which is the one and only Simconnect P3D4 (as the server) uses which is, of course, the P3D4 Simconnect *server*
That's the one and only Simconnect the sim runs with so yes, you have it installed, because that's what the sim comes with by default.
This server can accept connection from ANY Simconnect client (FSX, P3D1, 2 and 3), which are the various add-ons which were programmed to use one of these Simconnect versions. But if you never installed any of these on a clean system, you are missing the CLIENT runtimes.
That's why there's a redist folder in the sim, which allow you to optionally install the various Simconnect clients runtimes, so you can run add-ons that are programmed to work with FSX and older P3D versions as well.
If you installed only add-ons that were made to connect only with P3D4, you didn't had to install the other clients: those addons could connect with the P3D4 Simconnect server, because the P3D4 Simconnect client is automatically installed by default, and that's what made you to assume "Simconnect is no longer required", which is not obviously the case.
And no, before you ask, Addons using the P3D4-version of Simconnect won't run "better" just because they use the same version, since it's just a matter of the number of functions available to them, since older versions had less functions, but we already solved this, by having a small .DLL in our software that acts as a bridge to allow calling the missing functions which we might need, which is easier to maintain, since it's very small and manageable.
This allows us to run almost the same client software except for the Addon Manager .DLL, which is a fully native P3D4 app that also use the more "native" PDK AND the P3D4 version of Simconnect, and keep the rest of all the other software backward compatible with FSX SP2, FSX:SE, P3D 1, 2, 3 and 4, without having to have separate versions of the executables for each supported sim.