Mythic Hero predictions?

Astra is an adaptation of Latin's "astrum" meaning star.

Camilla or another Lyn

Jokes aside, i think Alm finally will get his "special" alt

For Astra, Elincia maybe? Her affinity was Heaven in RD so maybe Astra will equate to Heaven.

Well, we're bound to get heroes from each game at least.

Eliwood like you said feels like Anima.

Micaiah is obligatorily dark.

And Seliph is for Sure Light.

However, we still have more spaces for Legendary Heroes, so I'm not going to guess alot until the LHB slots are filled up,

Sephiran for Light (I made him a long time ago, before Light Mythic heroes were to be a thing; Saber's Golden Dagger actually uses a mechanic I came up with on Sephiran beforehand, too):
https://project-emblem.wikia.com/wiki/Sephiran_(Ashera's_Counsel)

Stats: /41/ /31/ /35/ /14/ /27/

Staff: Ashera (14 Mt) - Grants Def +5. Slows Special trigger (cooldown count +1). The enemy cannot counterattack. At start of combat, if unit's special is charged, unit can counterattack regardless of foe's range and abilities. When healing Special is triggered, replenishes the HP and/or removes the stat penalties of all allies healed/boosted (respectively). (This skill cannot be inherited.)

Assist: Healing Push+ - Slows Special trigger (cooldown count +1). Restores HP = 50% of Atk - 5. (Minimum of 5 HP.) Grants another action to target unit if it performed action this turn, but it can only move one space and cannot attack or assist if it performed either this turn. Sing or Dance cannot be used on this unit.

Special: Ordering Light+ (CD: 3) - Grants unit +3 Light blessing. (In order, only Hero status or highest or first affinity applies. Does not stack.) When healing an ally with a staff, restores 10 HP to all allies and grants Atk/Spd/Def/Res +2 to all allies for 1 turn.

A: Mantle - If foe initiates combat, grants Def/Res +4 during combat. At start of combat, if foe initiates combat and unit's special is charged, inflicts Special cooldown charge -1 on foe per attack. (Only highest value applied. Does not stack). (This skill cannot be inherited.)

B: Lulling Corona - Grants Light Hero to unit and Def +3 to all allies with 3+ Light affinity. (In order, only Hero status or highest or first affinity applies. Does not stack.) Inflicts Atk/Spd -5 on foe through its next action after combat. If unit initiates combat, inflicts Spd/Res -5 on foe during combat and calculates damage from unit's staff like other weapons. (This skill cannot be inherited.)

C: Rewarp - Once per turn after unit performs first action, if unit did not perform assist or attack and unit and all foes are outside mutual immediate attack range, unit is granted another action. (Additional action granted once per turn only.) (Cannot be inherited by cavalry, flier, sword, lance, dagger, dragon, bow, or dagger units.)

I'm genuinely confused as to why Micaiah wouldn't be light instead of dark?

we will get another Ryouma for Astra.
because he is an astra crit machine in fates.

If Celica isn't the last fire legendary I think she goes here. Back in CYL2 it was said that since she's in her Gaiden outfit there the full-out royal outfit needs to appear and she'll be a legendary sooner or later.

I'm guessing we have it all wrong. It could be new and unique characters that have nothing to do with the rest of the series, or crossovers, or non-protag legendary-like heroes. I wouldn't speculate until we get our second mythic hero.

A guiding star... One who led others i imagine