We can’t lose sight of the fact that he is their best LD by far and is not arbitration eligible. The flat cap means that the risk of an offer sheet is fairly low and, absent an offer sheet, he can accept a bridge deal, accept his qualifying offer or sit. He doesn’t have a lot of options and could do worse than signing a one or two year deal and cash in bigger when the cap goes up.
For all the reasons you stated, I'd say there is about a 95% chance that he starts next season as a Ranger.
However, their cap situation in the short-to-medium term is pretty rough. Panarin, Zibby, Trocheck, Kreider and Trouba combine for $40.267M in 3+ year long cap commitments who currently have full NMCs. Fox is at $9.5M long term and isn't being moved. Shesterkkn is at $5.67M for 2 years and isn't being moved. That's $55.427M of cap on just 7 players that absolutely isn't going anywhere to make space for a Miller extension. Kreider and Trocheck's trade protection weakens in 2024/25 and 2025/26 respectively, but Shesterkin will be due a large raise in 2025/26. Goodrow is the most obvious candidate to shed some salary, but he has a 15 team no-trade list and his $3.6M cap hit for 4 more years probably makes him a negative-value asset.
If (and this is a big if) Miller is currently telling him that he will use every tool at his disposal to get a 5+ year long deal at $7M+ and won't accept anything less until days before the 12/1/23 deadline, then it would make sense for the Rangers to quietly see if a team blows them away with an offer. Signing him to such a deal (or matching an offer sheet like that) would require them to move at least 1 good asset out (either a player like Chytil/Lindgren or whatever it takes to move Goodrow). I think there are trade packages you can offer them to make it more appealing to let Miller walk than to keep Miller AND lose more stuff.
If Miller is content to sign a 2 or 3 year bridge and then cash in with a higher cap, then he will absolutely not be available. A 2 year bridge gets the Rangers through the worst of the trade protection they've given out and gives them time to move a genuinely big contract to fit his monster deal. Panarin's $11.6M and Trouba's $8M come off the books naturally in 3 years so a 3 year bridge would mean that they simply have to re-allocate that $19.6M with Miller getting a nice chunk.
Players signing offer sheets rarely happens, but I think that the threat of offer sheets, and RFA negotiations (without a signed offer sheet) impact negotiations more than people think. Let's say the Blues were offering the #10 overall, the #29 overall, and one of our 2023 3rds for MIller's rights at the moment. you can nudge them toward negotiating by telling them that we have every intention of calling Miller's agent on July 1st and offering $7M x 6 years. The compensation on that is our 1st, 2nd, and 3rd round picks in 2024. The trade offer we're making today is clearly better than the compensation unless the Blues truly bottom out and have a top 5 pick next year. If Miller's agent is currently telling the team that he won't even consider a bridge until talking to teams in July, then the Rangers have a decision to make: commit to doing what it takes to ensure that they can match such an offer in the summer or negotiate a trade right now. Such a scenario likely doesn't lead to an actual offer sheet, but the threat of one gives the player leverage.
Again, I think you are right that he has very little chance of wearing any other jersey next season. He very well might want to bet on himself to take another step as a player and get a $10M+ AAV in 2 years rather than locking in generational wealth but potentially leaving millions on the table right now. There are a lot of paths that leave Miller discussions fully moot, but until he signs or the Rangers start blocking Army's number, he shouldn't be off the table.
Why would waste 3 first round picks on signing Miller?
You can likely trade one or two first round picks and get a top pairing defensemen without PO another GM by signing a RFA.
Signing RFA....that always seems to work out well for the Blues.......
Like I said above, all 3 firsts is too rich for my blood.
However, the logic of paying more for Miller than trading less for a different to pair D is that he is the higher value asset than whichever other top pair guy you can plausibly acquire via trade. He has the greatest chance of being a true #1 D man of all the guys who are potentially available via trade. He's a 23 year old 6'5" D man who can skate very well and was just 12th among all NHL D in even strength scoring with positive underlying metrics despite an O-zone start rate of just 41% at 5 on5.