I totally get the whole idea of it likely being Hunter, mainly because why would he have left and come here otherwise...but if that was the case, it really doesn't make sense why they have Nonis here still. The only reason you leave Nonis in place, is if you're hoping for someone that isn't available to become available in the off-season imo.
Plus, there was that rumor that Shanny wanted Blake, which wouldn't have come up if it was promised to Hunter already. Unless of course that was totally made up, but it doesn't seem like.
Think there's a few reasons why Nonis is still here, and you've named a few of them:
1 - Nonis is the only exec in that front office with tangible NHL experience & knowledge right now. Could Shanahan and co. be relying on that expertise? Most definitely.
2 - Does it make sense to fire him right now? Close to the deadline, where you need his league sources & contacts and ability to hit the phones and make deals, firing Nonis now would be counter-productive.
3 - Shanahan and company don't know what they want to do with him yet - fire him? Keep him? I don't think they are anywhere close to being sure what do do. Could Shanahan be biding his time, to make sure that not only does he get a good feel for what Nonis is about, but what Hunter & Dubas are about as well, especially regarding being future GMs?
4 - Shanahan can hide behind Nonis for now. So long as the GM is there, the heat is on him and not on Shanahan. Brendan had 2 silver bullets in his gun. He used one on Randy in January. Once he inevitably uses his 2nd one on Nonis, the spotlight & focus will shift to Shanny.
5 - Much easier to conduct a more thorough search for both coach and GM in the off-season, when there are more candidates and less urgency to make a decision.