Will all cosmetics we see each month be available post launch for embers ?
Nope. These are exclusive to the month.
You're helping us build the world though, so you may see variants of these creatures, outfits, and buildings in the world as NPCs and NPC structures, but no one else will be able to attain them.
That said, we'll have plenty of other awesome and cool things for folks to get through adventuring in the world of Verra! <3