We can't really know for sure about promotions. In the Japanese version of Radiant Dawn, to go from Tier 2 to Tier 3, you needed to use a Master Crown. You couldn't just level to 21. In other words, the reason there were no promotion items in the English games was that NoE/NoA felt they were unecessary and removed them.
Similar to Radiant Dawn, Awakening has Master Seals as promotion items this time around, and you have to use them to level up. This might be removed in the English version, so we can't know. I find that relatively unlikely, though, as there's also a second class-change item that lets to reclass your character, and having that and no Master Seal might end up being odd. So, overall, so far, it's unlikely there will be a "promote instantly at level 21".
And as far as I know, there's no canto (remove after attack as a mount) at all. That isn't a system implemented for the first time in Path of Radiance anyway, but one from Fire Emblem 4 originally. They've gone with the route of there being canto in the console versions, and there not being any in the handheld versions. In this game, canto would be a bit odd due to the dual-attack mechanics, as well.
