Does anybody know if the Elysian drop troops will e included in the CR? Or will they be a possibility for add-ons?

Honestly, we don't have a clue what regiments will be. Or even how they will be handled yet (i.e. - Like Chapters in Deathwatch? Rogue Trader Dynasties? Something freeform that your group creates?). there isn't much in the way of info. Compare to Black Crusade or Deathwatch where by this point we'd had a wealth of previews already. Right now we pretty much only know the game exists, and is about the guard, and 8 of the Specialties because they've been named in the marketing previews.

^^This…

However, they have, over time, become a more popular regiment, even getting some really pricey, er… pretty Forge World minis. Several home-brewed regiments are said to be someone combined with them, and so is mine, the 1st Lokarin Skyshock Drop Troops (combination of the Cadian 1981st and the Elysian 103rd).

I think a part of this might have to do with their ability to field fewer tanks, potentially a big logistical nightmare, and maybe a financial pain for the player (if they weren't buying FW minis). Due to that, I think that they actually might get a mention, either as an option that doesn't need the big guns, or even if they choose to leave out the tanks from the core book, to again show how IG DON'T NEED tanks (though they help).