The case where the mike hole becomes empty the back had been exhibited to similar iPad (5th generation) in that. The thickness speaks to a certain manufacturer iPad mini (2nd generation) that the thickness increases from 7.2mm of iPad mini to 7.5mm. Moreover, the width seems to extend more than iPad mini by 0.2mm, too.
Notably, the third generation iPad saw its thickness slightly increase when updated with a Retina Display so the rumor is plausible.
Apple is expected to unveil the iPad 5 and Retina Display iPad mini 2 on October 22nd.