Larian Studios Forums Divinity 2 - Ego Draconis (English) Divinity 2 - Ego Draconis Divinity 3 / Episode 2 [beware of spoilers!]

The original words sounds like: "we will get the continuation of the story in next year". Story/plot of DD2. So, I guess, it's a sequel.

P.S. Any addon or mod can be sequel. "Sequel" is a plot/story-related thing, addon/mod is a content/container-related thing. Meaning differs.