Just like everything else, methods of crime will change as well. People will start hitting delivery trucks, mailboxes, and postal workers. There's a hundred different ways to run mail order scams too.
Instead of taking the item from the store, now they'll use your grandmother's debit card to have it ordered to a vacant house. You can buy somebody's full personal information online for less than $20, including credit card numbers, pins, SSN's, and everything else. As shoplifting decreases, we will see a massive rise in internet crime, which is unfortunately much harder to prosecute, because usually it's multi-jurisdictional. It would be easier, and safer, for me to buy your grandma's personal information online and drain her checking account, then it would be to physically drive to a store and steal something.
I think it would be much more effective to tighten security at stores instead. Keeping expensive items in locked cases, using those "spider tags" that make it really obvious when somebody walks out of the door with an unpaid item, and change the law to allow loss prevention to physically stop a shoplifter.
The real problem isn't the shoplifting itself, it's the morality of a society that doesn't care anymore. People aren't just born criminals, they develop into them through their environment. We need to change the environment if we need want to change the quality of person.