All About That Bass is not eligible. Shake It Off will definetely be nominated, along with Uptown Funk.
Not necessarily, though. Last year "Royals" was not supposed to be eligible, yet MTV did some voodoo and got it nominated. Also, this the MTV.com video for AATB says it was posted on July 14, which would make it eligible, I think....
For me the best videos that deserve to be nominated are Blank Sapce, Anaconda, The Heart Wants What It Wants, I Want You To Know, Only, 7/11, This Is How We Do.
Brit/Iggy's vid, Nicki/David's video also coming.
Also vids by Rih/Selena/Miley coming. I think its too early to tell.