I doubt. They always try to encourage people to do at least Normal. Imo it would feel pretty shit if you (as casual/newbie) learn/prepare for fights, go outside your comfort zone to find group for raid and your buddy Steve was like "lol dude what are you doing, just click this button and you will be done in 2 hours half AFK". Of course better loot is always good encouragement, but I think simple curiosity and desire to "complete" instance is far stronger incentive.
Maaybe they will release 1st wing with Normal/Heroic/Mythic, but that's it.