Alright that's gonna be a long essay.
The Story So Far:
https://www.youtube.com/watch?v=pVYeJyZCwzE
Daddy Sakurai tweet:
https://twitter.com/Sora_Sakurai/status/1027234926167388160
Sakurai is teasing Isaac for those reasons.
First we have 3 characters in an arena, in GS, if you play against a friend, you can only use 3 characters instead of 4 since the GBA can't handle 8 adepts.
Second, why Link, Marth and Shulk in this order? They are shown from oldest to newest, and we can replace them by your first 3 party members in Golden Sun. Link = Isaac, both are silent protagonist. Marth = Garet, Marth come from FIRE Emblem and Garet controls fire. Shulk = Yvan, both can see into the FUTURE.
Sorry if someone has pointed this out before, but I think I’m seeing something with this tweet. Link is 64, Marth is Melee, Shulk is 4. What’s missing? Brawl. Who made their smash debut is Brawl? Isaac.
Thank you Silo for that new piece of evidence, it make sense, just like the list of Trophy whit Isaac missing, someone from Brawl is missing!
Beside, this angle is rarelly used in RPG, Camelot is one of the only studio using it. What a coincidence...
I believe that Rathalos may be a reference to the Fusion Dragon, the final boss in Golden Sun, why? Both the Fusion Dragon and the Rathalos use fire attack and both can poison. Beside the fusion dragon comes from the fusion of two Mars adepts (mars adepts controls fire like Garet) And in Monster Hunter, the Rathalos drops can be use to make Fire Weapon, while the Rathian (the female) is use to make poison weapons. So Rathalos is more link to fire then poison, just like the Fusion Dragon.
Beside it's not the first time that Sakurai has use Twitter to tease a character, he did it whit Palutena, Shulk, Bayonneta, and Simon/King K Roll (red eyes) He even put a freaking red and yellow barell during E3 were he was getting record to tease King K Roll early, so it would not be the first time. Finally Golden Sun Dark Dawn page was update twice in the past weeks, it was the first time in years. (It may very well be nothing thought). It's a little too much if you want my opinion. Latelly, just before Loz18 Twitter d, he said that Isaac may be in after all (no confirmation).
https://twitter.com/MimiqueVEVO/status/1031718391260700678
Also this guy who has a track recored of getting this right
Hmm, is the Sun going to rise again?
Who Mimique is:
https://www.youtube.com/watch?v=ecv3M5_TY_I (Link from
T
ThoughtfulWanderer
Apparently he said that Rathalos and Shovel Knight were AT, maybe he is a leaker disguise as a guesser.
Hoping for an happy ending.
Edit: Like I said, when something seems obvious in life, it's because it's happening.