Thanks for the posts!
The NAS I'm looking at is a Synology DS413 with a Freescale MPC8544E PowerQUICC III.
The NAS also "offically" supports up to 16TB with 4 bays. Even the older DS411 supports 16TB. Looking back in time, Synology NAS made in 2010+(ARM) and 2008+(Intel) offically support large 4TB drives now that didn't exist back then.http://originwww.synology.com/support/hd.php?lang=enu&bays_id=3
So it seems safe if the HD & controller is SATA with 48-bit LBA and the OS supports 16TB partitions, then the NAS "could" scale much higher.
The point to all this is I don't want to buy a power hungry 12 bay NAS, then only need 4 bays when the bigger drives come out. The timing on the next hard-drive generation is bad for me. This will be for home use for large amounts of uncompressed video, do I don't need many simultaneous users on 24/7.