It looks like Bauza is leaving, the new AFA leaders seem to be going all in for Sampaoli. Unfortunately, the problem of the backup plan still lingers. Gallardo said that he's not interested in coaching the NT right now while Berizzo seems to be overlooked as a choice, doubt the AFA will go for him. Other than those two, I can't imagine any realistic options that'd be good for them (Simeone not being realistic).
If this is the case, then it's a necessity for Sampaoli to say yes. It's up in the air at the moment, but this would be a true change to the Argentine NT. I'm really curious to see how Sampaoli would utilize Messi and if he can stimulate some decent form out of Aguero, Di Maria, etc.
I hadn't considered the case of a coach working with both a club and the NT. If they have good staffs for both teams who can handle some responsibility, then I'm sure it's doable in theory. For example, the club's assistant manager would have to handle most of the work/prep during international breaks. Sampaoli has a fairly capable assistant manager at Sevilla in Lillo so that could work. I don't know if it'd be considered, haven't read anything in the media about a dual coaching job being on the table for Sampaoli.