This. Happens. Every. Single. Codex.
The sky will fall and everyone freaks out about how over powered the newest dex will be. Frankly, I've heard nothing that is truly concerning or cannot be planned around. I'll get a copy of the codex and I'll look it over. Not to start playing nids or to complain forever about the gross injustices and codex creep.
Instead, be proactive about this change. Find the weaknesses in this codex. Is it time for plasma to make its return - due to the difficulty of hiding something as large as a trygon in cover? Powerfists will appear in just about every single squad that can equip one. And finally, weapons and abilities that inflict instant death (S10 Pie Plates, Force Weapons, Skulltaker, Wraithcannons, etc) will be somewhat popular again due to the loss of Eternal Warrior.