The Spells you have now aren’t changing in rarity, they will stay the same.
So if you have a Mythic Spell, it will still be a Mythic spell but you can now increase it’s rarity another 2 rarities.
If you have any Legendary Spells, it will stay a Legendary spell. No Spell is getting an increase/decrease in their rarity in this update, so none will be transformed into X+ rarity.
The level of a spell before 2.5 (I believe) is irrelevant, as we are removing spell levels and why we will be sending back those level resources - the focus is on the Spell rarity and now your Spellbook level.
As for Season Spells, it is not 200 coins a Page, it is 200 coins for x5 pages.
