I think the onward march of phone sizes into the 6" range is cannibalizing the market for small tablets, and 9-10" for tablets is the remaining sweet spot between phones and laptops.
Given the Nexus 6, I actually think this is too small. If I'm going to have a six inch phone, I'd prefer a tablet that is upwards of 12". I think huge tablets are currently an unexplored niche that could kick off just like big phones did.
Unless apps are specifically designed for 12" screen and they work like traditional desktop I am not buying them. A screen as big as 12" needs to multitask. It has to has a dedicated taskbar not clicking the 3rd button to bring a bunch of backstack windows.