We've already got the Nexus 6, so no need for another phablet this year (unless they make 2 models). My personal preferences (which I'm sure we won't get):
Screen: 4.7-5", no larger, 1080p, and I'd actually prefer a good LCD (lot of white in Lollipop, while AMOLED works better with dark).
Battery: 3000 mAh or higher. Can never have too much really.
SoC: I care more what cores are used than how many. If the Snapdragon 820 is available in time and the Kryo core turns out to be any good then that would be the obvious choice. Best have a decent gpu too.
Storage: 64GB minimum (and I would prefer expansion, though you'll never get that from a Nexus).
Camera: I care far more about dynamic range and noise levels than pixel count, so somewhere around 13MP should be fine. Give me separate control over noise reduction and sharpening, and raw output as an option. If you want to shake it up, see whether you can fit a modest optical zoom into the package (may require the right-angled optics some compact cameras use, and rules out extreme thinness).
Front camera: really don't care, but stupidly high resolution here doesn't make sense to me.
Radio reception: rarely mentioned, but has to be a priority. Moto have a reputation for being good, and I can say from experience that recent high-end HTCs are, so if we're choosing manufacturers that's a vote for one of them.
Sound: dual front-facing speakers and a good quality headphone output.
Extras: Qualcomm's talk of a fingerprint scanner that can be embedded under the cover glass is interesting. I'd also like a high IP rating.
Colour: give a few options, but I like dark phones.
Doesn't need to be blade-thin either.