Well its obviously a sequel, its based in the same universe. It links heavily to the last two games. What else defines a sequel?
I'm not happy they seem to killed off Revan's Char however, they kinda killed any chance for a Kotor 3 invovling finding revan. But o well.
Milt's right though old republic is a big era, it really didn't end til the middle of ROTS. the Old republic is 20,000 years old and theres 4000 years from Kotor 1 to ROTS.