Funny part is that a Finger Print Scanner would make the most sense on an iPad as many use them for bank transactions, heavier web browsing (much longer sessions) which can entail viewing more sensitive data, documents etc...also considering in many homes iPads are shared, so the account payer may want more security control, but a part of me also believes it might not make it in, simply due to the possible production difficulties.
I think Apple would love to have a finger print scanner on both 5S and iPad5, reason? Well many people stuck with the iPad2, I have actually seen more iPad2s than iPad 4 TBH. So, a finger print scanner would add that bit more incentive, on top of Retina Display, A7 chip, bigger battery and a whole new design. The iPad 5 is going to be a very important product as it brings in a new design.