Q10 Pro will support up to 6TB internal Hardrive according to the Himedia's Youtube video clip.
Please read my tutorial in the general section on this topic first. Lots of incorrect information floating around about this including on this forum, There is no real new boundary between 2 TB and 16 TB. There is a big one at 2.2 TB though and another one at 17.6 TB to be precise. After reading you understand how and why. A product has the right drivers or does not. For Internal a 64-bit register GPT driver is needed and for External USB the driver needs to support 4K sectors.
My educated guess is that 8 / 10 TB will work just fine both Internal and via USB. Official support is what they tested nothing more or less.
Running 6 TB disks my self even with 5 year old media players both Internal as via USB (official 3 TB Internal only).
Don't own any Himedia products myself but probably applicable to most if not all current products. Just be brave and try it, never came across a case where 3 TB worked and 6/8 TB did not, this regardless official support specifications!