Not confirmed that entire game will be Source 2 based but they are certainly working on elements of it.
https://www.reddit.com/r/The_Gaben/comments/5olhj4/hi_im_gab...
https://www.pcgamesn.com/counter-strike-global-offensive/csg...
Although this is from the Chinese press conference, and Valve hasn't confirmed it officially, it's at least credible.
Do you have source for this?