Does anyone have a recommendation on a reasonably high end Android tablet that will receive ongoing updates/upgrades.
I'm looking for an 8 to 10 inch device that has at least 4G RAM and 64GB storage.
Ongoing updates? - yes, currently on Oreo.
Screen? - 10.2"
Not sure why you want 4+ GB RAM since the android ecosystem doesn't really have any apps that can utilise it. 3GB is enough for all the multitasking you could want on an Android device for the useful lifetime of a tablet right now and the 6GB models are just marketing fluff, unless the whole app ecosystem of the Play Store changes. What matters more than RAM is actually the NAND speed and the efficiency of the OS. Google does very well in this department, for example - side by side comparisons of the 3GB Pixel XL has it running heavy tasks quicker than the 4GB S7 Edge. Samsung's extra RAM is going unused whilst the lighter, more nimble OS with less bloatware and faster storage subsystem is what actually matters in real-world usage.
If you check the memory usage of your current phone/tablet - it will likely show that about 80% of it is in use right now. That's simply because Android system doesn't reclaim memory from background applications until it needs it - putting them into various states of idle/sleep/hibernate to NAND on the fly as needed. With an active tasks app monitor installed, I'm running about 10 regular apps on my phone and the actual memory usage of those active apps is a little over 300MB.
If, for some edge-case usage that I haven't covered, you still want more RAM, the only sensible options are the Samsung Galaxy Tab S3 (4GB) and the Asus Zenpad 3S (4GB) but they will generally be slower than the Pixel and also suffer from inferior build quality, sound quality, screen quality, and interface quality. The Pixel C is expensive because it's just a much higher-end product.