I would actually vote against having a larger screen. There comes a point when it's not a phone, it's a tablet, and I think that Google and the Google ecosystem would do well to remember that.
Screens from 4.3" - 4.7" (10.9 - 11.9 cm) are really ideal because they give you enough real estate for a phone, but they're not too big for too many people's hands out there. Once you start talking about 5" (12.7 cm) and up, to my mind that's really starting to get too awkward.
Beyond that, I would only look for a few things:
? Higher-capacity battery so folks could go 2.5 - 3 days between charges;
? LTE (of course);
? 32GB and 64GB (maybe even a 128GB) option;
? Edge- or front-facing stereo speakers
I don't know whether Google's use of the EXTfs rules out them *ever* using microSD again, but I'd not mind if they did go back to microSD for storage. Other than that, if the thing is freaking huge enough in terms of capacity, it might not really matter all that much.
Oh, and I would wish that Google would start using PNG as the default image format, not JPG.