Don't let the facts get in the way...you just answered your own observation. Sure everyone in the NHL knows he is going to California, but there are three teams in California who would love his services. San Jose needs a knew identity, Anaheim is looking for a top 2 defenseman since Niedermayer retired for good. Los Angeles may be a piece or two away from making a serious run at the Cup. So even though a trade scenario would probably only involve three teams, if all three of those teams want him, then you may be able to get something of value in return. Ryan Clowe may be a stretch, but if all three teams are interested, he will get us more than a lower round draft pick. Quincey garnered a 1st round pick, Stuart is a bit more valuable than Quincey on the market...Fact.
SJ already has Boyle, Vlasic, Burns, Demers, and Murray signed for next season. They also have Braun as an RFA. In total the Sharks have $8.7M in cap space with 9 players to sign (they only have 7 forwards).
ANA already has Visnovsky, Sbisa, Lydman, Beauchemin and Fowler signed for next season.
LA already has Doughty, Scuderi, Mitchell, Greene, Voynov, Martinez and Drewskie signed for next season.
None of those teams are in a position where they would trade for the negotiating rights to Stuart. Even if the Sharks do want a new identity (on their blueline, which clearly isn't the real problem) I can't see them handcuffing themselves by trading for Stuart's rights and then either having to give away one of their current top 5 or be stuck over spending on their blueline.
Anaheim could possibly be interested in Stuart but they're already committed to 5 quality (in their mind) blueliners. If they want to supplement what they already have I don't see why they'd be giving anything up for a chance to sign Stuart. If it's clearly already known that Stuart wants back in with one of the California teams (which obviously that seems fairly apparent) I think the Ducks easily take notice of the fact that they are the only ones with cap space and roster space that makes sense.
LA has 7 d signed for next year. Stuart isn't much of, if at all, an upgrade over their current top 4 (despite what some Wings fans may feel). Stuart is probably a lateral move between the Greene's, Scuderi's and Mitchell's of that roster. Plus, the Kings were willing to lose Jack Johnson off their blueline because they like their kids (Voynov and Martinez) so much. No way the Kings sign Stuart, let alone trade anything for his negotiating rights.