Sounds like you are referencing an old test build.
Production (Official) is at 10586.420 since yesterday.
If your phone is on the eligible list and not waiting for carrier approval (branded phones) use Upgrade Advisor to get the Official release (RTM).
If you use Insider on the Release Ring, the same version is fetched as the recent public Upgrade received by these phones (10.0.10586.xxx): Phones Eligible for Windows 10 Mobile Official
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.
Check out this thread: Windows Insider Testing and You [Recommended Guidelines]
For right now, Windows Device Recovery Tool is only flashing 8.1 to models that did not launch with 10 so it is the way to revert if you don't care for W10M: How can I recover/reset/restore my phone software?
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