AIUI if you buy now you will be able to take advantage of the reduced price upgrades so won't be paying the full price for version 3. And if you find that Version 2.6 does all that you want then you have no need to upgrade.
Also, you have spent a significant amount of money on a mount, an OTA, a guiding system, a focuser and a camera. Maybe a filter wheel and filters as well. That lot will easily come to several thousand dollars. Even if you try to spend as much money as you can on SGP you will find it difficult to spend more than 5% to 10% of the cost of the hardware.
Good software is very time consuming to write, debug and document. SGP isn't perfect but it's backed up by a couple of dedicated developers who strive to get it closer to perfection. Occasionally they need to eat.
If you are really short of money then I suggest not getting SGP at all. You can operate perfectly well by using the image acquisition software provide by the camera manufacturer, and monitoring your system, watching what is happening, and changing or adjusting things as needed.