Welcome to Android Central! Only Google can answer that. It's a gargantuan company, and they have tons of projects going on. Maybe they weren't satisfied with Qualcomm's new Snapdragon 3100 chip (which has mostly underwhelmed tech pundits). Maybe they were far along in the design, and then scrapped it because it just wasn't working out. Maybe they know of a better chip coming down the line in a year or so, and decided to postpone until it was available.