This is spot on. The rumors were already swirling before his announcement that the 16 was going to be lacking funding even more than usual. Seems like it was probably more of a mutual decision between Biff and the organization more than Biff just putting his hands up and saying "I quit".
Crazy to think about it though, how Biffle ending up being the last man standing from the Roush golden era after the departure of Mark Martin, Edwards, and Kenseth. All those guys to me "were" Roush, and they all left. I mean Kurt got fired, but the rest all saw the writing on the wall and sought better opportunities. If Biffle does indeed retire then it'll be sad that he didn't get the second chance like Kenseth and Edwards got with Gibbs, or get to go around and have some fun whoring himself out like Mark did to end his career. Fading away versus burning out, you know?