If your phone is not on the supported list, then 10586.xxx (Threshold) is the end of the line. You may as well use Insider and select Production to un-enroll your phone from Insider, but at least you have W10M. WaaS (Windows as a Service) will deliver future updates within Threshold to you without any Insider access required.
If your phone is on the eligible list and you go Insider and stay on the Release ring you get the next public version early as Release ring in effect is the RTM. This will deliver the most stable Redstone builds to you earlier than OTA push with minimal risk.