A good proportion of the yeast that settles out is flocculated, dormant yeast. Even after a good few weeks in primary, and also after a cold crash, when it seems like there's a lot of trub settled, there is still going to be yeast in suspension. The yeast cake can be harvested and used for future batches. Check out yeast rinsing/washing and harvesting threads if you're interested.
You should be fine for carbonation with an ambient temperature of about 70*F to help revitalise the yeast.