That's pretty much confirmed, that it will be 64-bit. Especially when NVIDIA leaked out that they are working with HTC and Google on the Nexus 9 which will feature the Tegra K1 processor inside. So it'll be 64-bit, but we likely won't see much in terms of speed changes. Why? Because the Nexus 9 more than likely won't have 4GB of RAM. I don't see Google jumping from 2GB to 4GB of RAM, but it can be done. And Samsung is already mass manufacturing 4GB of RAM modules for mobile devices - which made it odd that the Galaxy Note 4 didn't have 4GB of RAM.
Android L, which will likely launch on the Nexus 9, is going to be 64-bit and now the Nexus 9 will have the correct hardware to support it, which is a big deal I think. The NVIDIA Tegra K1 is also a big deal for gamers. As you'll get all kinds of amazing graphics and such for gaming on Android. So I fully expect that Google will promote this as a gaming device, if they don't, I'd be very surprised.
The Nexus 9 is shaping up to be a pretty interesting tablet from Google and HTC (HTC is also rumored to be launching a few more tablets this year). I'm definitely looking forward to it. How about the rest of you?