If you're considering upgrading from the iMX6, then the Q7 (quad core CPU and more RAM) or T8 (quad core CPU, octocore GPU and more RAM) would make sense.
Should you be looking at getting an UltraHD (4K) TV in the next couple of years, the T8 is the only device capable of above 1080p resolutions.
If you only ever watch 720p or lower resolution videos, don't use the iMX6 for gaming at all, and never found yourself wishing the interface was a little more snappy to respond, then it sounds like the iMX6 still meets your needs.