Ive been thinking about how the musketeers are like spiritual far cousins or whatever you wanna call it, of the Johto beasts, with them sharing similar personalities (proud, aggressive, feminine ~), being the second quadruped trio, found scattered across the region (in a different manner I know), share NO type with them... freaky things like sharing the exact same heights (Cobalion/Entei 2.1m, Terrakion/Raikou 2m, Virizion/Suicune 1.9m)... and how ones were born from dying in a fire, while the others saved wild pokemon from dying in fire. lol
So what if Sinnoh basically finished the "first round", and made 3 Psychics as a special trio to point that out?
Then perhaps gen VI and gen VII would see trios that are in some vague way equivalents of the Kanto birds and Hoenn golems?
Anyhow, heres my guess from this xDDDD
A trio of nature-related birds:
Grass/Flying
Water/Flying
Ground/Flying
(with a hidden fourth event member like Keldeo... Normal/Flying?)
Or something more abstract, perhaps some specific kind of liquid creatures (think Heatran or something? xD)
Water (water..)
Poison (acid)
Ground (mud)
(and then gen VIII in Sinnoh-style, but make 3 Ghosts or 3 Bugs that time instead? I'm definitely looking too much into this I know! LOL....)
As for the "extras"...
Id love to see some special legendary that controls gravity, lol.
Or a plasma-related one.
And temperature shifter?
Like, make it Normal/Psychic, but then depending on specific triggers, it turns to either to Ice/Psychic or Fire/Psychic...either turning slow and defensive, or fast and offensive.
xD
They'll prolly make something with a concept that can easily spawn interesting formes in later games.