Not sure what you mean by this?
The stock solo ArduCopter firmware is cira 2015. It is not supported anymore, and heavily customized in manner that makes it very difficult to modify or upgrade. The stock pixhawk 2.0 is also circla 2015. And the stock motor pods have an electrical flaw because the CEO of 3DR was too cheap to do it right. That is reality.
The Pixhawk 2.1 is the current and heavily supported hardware, and will be for a long time to come. ArduCopter 3.5 is the current and heavily supported version of firmware for it that will be for a long time to come. The Green Cube mitigates the motor pod electrical flaw so you don't crash. That's reality. Nobody is trying to "force" the green cube upgrade. It is the hardware required to run the firmware required.
If someone wants to volunteer immense hours of their personal free time to try backporting some upgrades from ArduCopter 3.5 into the old stock firmware, they are more than welcome to take on that hornets nests. Are you volunteering? Nobody is stopping someone from doing that. But do not expect those of use already working on this to steer clear of reality and work backwards in addition to forwards. There are not enough hours in the day, nor gallons beer required.
That said, there are plenty of updates coming that do not involve ArduCopter in any way. Updates to the controller, applications (solex), the IMX, etc. Most of those are backwards compatible with the stock cube and FW because they have nothing to do with them. So it is likely you will see installation packages for stock hardware and installation packages for Green Cube hardware. The latter will have ArduCopter 3.5.x. The former will have the old stock version. Stock hardware simply doesn't get any of the benefits of ArduCopter 3.5.x... like boat mode for example.