Considering that I've got two Moto X devices that I carry, both less than 3 months old, what would make me buy a third? It would have to include all of these features:
1. As many have said, better low light pictures.
2. Even though it is currently excellent, longer battery life. This could be via a processor improvement or slightly larger battery.
3. Assurances that the new device would receive updates that are almost as fast as a Nexus device.
4. Minor improvements to the screen without sacrificing battery life.
A "nice to have" would be:
5. Availability of a 64 GB model.
Bonus feature that would seal the deal for me:
6. A single device that covered all of the key bands for T-Mobile/AT&T/Sprint. Similar to what the Nexus 5 currently does, except it would need to support the new bands that will be in play later this year. For example LTE band support for 2/4/12 on T-Mobile, and 25/26/41/12 on Sprint.