The thing that will kill BitCoin is the very thing it's corner stone is made of: The Blockchain. Having 100+ Gig on a portable device for day to day transactions is very unrealistic unless the price of high volume storage and lightning fast broadband every where cost fractions of pennies.
This literally makes no sense. You don't need 100 gigs for a mobile wallet. You need maybe 25-50mb for a decent wallet...not sure where you are getting this from. I haven't used the Core client in a long time but back when I did yes you needed to download the whole blockchain, but I have a feeling that was more for functioning as a node as well. Could be wrong on that, but today you don't need to download the entire blockchain to use a wallet.