Microsoft's ambitious plan to bring full Windows 10 with x86 app emulation to ARM processors was announced in December 2016, and it was promised that the first devices would use Qualcomm's Snapdragon 835 chipset. The first devices announced were HP's Envy x2 and the ASUS NovaGo, and they shipped with Windows 10 version 1709, or the Fall Creators Update.
Obviously, Qualcomm has a newer flagship chipset out, the Snapdragon 845, and we know that Windows 10 will eventually support the new SoC. SD845-powered PCs are coming in the second half of 2018, but it appears that we'll have to wait for the next Windows 10 feature update, codenamed Redstone 5.
Microsoft released the Windows 10 April 2018 Update today, and has updated some of its documentation. According to the minimum processor requirements, version 1803 still only supports the Snapdragon 835. The page actually says that it was last updated on June 15, 2017, but this information was not previously available on there.
It's worth noting that the Snapdragon 835 chipset used in PCs is not the same one that's used in phones. PCs use the Snapdragon 835 Mobile PC Platform, and Qualcomm hasn't yet announced or listed the specs of a Snapdragon 845 Mobile PC Platform. The lack of support in Windows 10 version 1803 could be due to the new chipset not being finalized yet.
Early reviews of ARM-powered PCs have been mediocre at best, but most users understand that they're still first-generation products. In other words, it's going to be fun to see what the boost in performance from the next-generation processor will bring. One thing is for sure though, the next generation isn't here yet.