For one technology to replace another it must be better in some way. I want digital wallets to work since I am tired of have a wallet full of cards. Until it becomes close to universal it is no way better so it will not catch on. IMHO what Google should push is for rewards cards. Most people have at most 4 credit cards but a ton of rewards cards and id cards for things like the gym.
Here is what I would do with Google wallet.
1. Make it a service on the phone. It takes to long to pop up after the scan.
2. Get it into more stores and Gas pumps.
3. Vending machines. I never have cash and that is a real pain sometimes. Not all vending machines take credit cards.
4. Push for rewards cards on the phone.
5 Get Sonic Drive in to use it. Sonic has a pre pay card that gives you free stuff. Right now you have to print that out if I could manage all of that from Google wallet it would be great.... Yea this one is just for me.