With the new SDK, developers would be able to natively recompile their apps to run in 64-bit on ARM-based PCs like the ASUS NovaGo. This opens up app support for the platform, which previously only supported 32-bit apps. The potentially greater app compatibility is welcome, since this was one of the biggest drawbacks of Windows on Snapdragon devices. But whether you'll get the higher performance that you'd typically expect out of 64-bit apps will depend on the Snapdragon 835 CPU that powers the current generation of the PCs in question.
Connected PCs ship with Windows 10 S, but Microsoft has been offering free upgrades to Windows 10 Pro through 2019, making the OS more familiar and versatile. The ARM 64 SDK will be available for both Store apps and desktop versions (.exes). Ultimately, it'll be up to developers to decide whether they want to go to the trouble of recompiling their apps for Windows on Snapdragon, but Microsoft at least appears to be making strides in creating as open and useful a platform as possible.
Update: This article was edited to correct a spelling error. Erin's last name is Chapple, not Chappie. In addition, Microsoft announced in November that Windows 10 S will get free upgrades to Windows 10 Pro indefinitely.