I think it's justified.
- that is there is a new game
I find this one the easiest and most confident to call. Camelot and EPD2 are working. They have been for two years. They are working on something. It is 100% a video game for the Nintendo Switch. Hardly contestable, no? You don't sit around with nothing to show for it unless you're Retro.
Camelot makes Mario Golf/Tennis and Golden Sun. They theoretically could be doing Everybody's Golf or another non-Nintendo project, but as I said, EPD2, the group who has always worked with Camelot, has a timeline that matches exactly with Camelot's silence.
The other very safe assumption is that Camelot is working on Golden Sun over Mario Golf. We've talked this one to death on this thread and
I brought it up in my video. There's a lot of evidence, including this taking far longer than we would expect to put out a Mario Golf game with the assets and code of Mario Tennis already available, the copyright, the previous sales of those two franchises, the sales of Switch RPGs at the time, ect. It's far more likely that it's Golden Sun at this point, though we all acknowledge it could be Mario Golf.
And I suppose it would be hypothetically possible to assign Camelot and EPD2 to an entirely new IP for Nintendo, but everything about that seems far riskier. Unless the Takahashi siblings themselves pushed it, I can't imagine that's a possibility. There's so many interviews where they talk about how they love making RPGs, how the story of Golden Sun isn't finished, how they love when the fans enjoy their worlds. And they've literally never done this.
- that Nintendo cares about this game/and or the fanbase enough to inform Sakurai of its immanency (he would've had to know since last year), which means presumably not a remake, but an actual new game
It is true that we have no direct evidence of any information sharing or relationship, but I don't find it too absurd that Sakurai would know about it or that Nintendo would value it enough.
Some thoughts are that he clearly has friends around the industry, even outside of Nintendo (Kojima, Suda, ect) He also works in Tokyo instead of Kyoto. Even before he was a god-celebrity-figure, he had friends at IS who let him know about Roy and include him.
Furthermore, one of his oldest connections, a composer that he's repeatedly relied on for 20 years now and whose work he is very familiar with, would be doing soundtrack for this new game.
To the point about how much Nintendo would value Golden Sun and put his name down on a list of DLC, well, you've got the results of the fan campaigns/release for Ultimate hype/leaks (I would say very successful at bringing the franchise to the forefront, having been on the inside), and that comment that
Furukawa was looking to release more 3DS franchises to highlight the portability of the Switch. It's circumstantial, but it's telling me the circumstances are that guy at the top making all the relevant decisions took a look at their library of unused franchises and said "yeah gimme more of those ones that work good handheld like RPGs and Brain Age."
- that Nintendo has decided to push Isaac, when Nintendo pushing anyone is rare. And perhaps most critically
This is fair and true. Maybe 4 out of ~80 picks have been shill picks. Corrin, Byleth, Roy, arguably Greninja.
I suppose it helps then that Isaac has all the support and fan demand needed of a non-shill pick. We can see this in polls from 2015 and forum posts since Brawl. The thought is that being a shill possibility AND longtime fan demand would make an Adept a no-brainer.
- that all this stuff is not merely a long shot, otherwise people wouldn't be getting excited. Because let's be real, people don't generally get excited about things they believe are unlikely.
You seem to imply that these feelings are unsupported. I'll admit our expectations certainly can be
wrong or otherwise misinterpretations of the situations. Nothing's guaranteed. Everyone knows this and we're fully expecting to be disappointed again.
But I would say after looking at the evidence, the most logical response is a bit of hope/optimism.