The news about a pending "Interview" with Brennan is typical of a situation where you "offer" a target the opportunity to "explain" some things. Most of the time the defense lawyer doesn't agree to the interview. But Brennan has an "appearance" problem if he was to refuse.
I don't expect much will come of it, and nothing prevents his attorney from directing him to not answer certain questions posed. IMO, given that I think Brennan is the lead suspect at the "macro" level, I think this signals Durham is done. Brennan's info won't change anything.
In other words, the risks involved in such an interview (getting into deeper trouble) simply outweigh possible benefits (persuading the prosecutor to leave you alone) in most cases.
Note that this doesn't necessarily mean Durham has decided to charge Brennan, although it certainly appears Shipwrecked leans in that direction. I would very much like to see that, too. However, it remains possible that an interview could be offered just to wrap things up. The bottom line is, we can't read too much into this situation.