It depends on your deployment scope and the level of integration with your existing systems.
PassKit technology is ready today.
Typically what takes the time - especially with larger corporates - is securing management buy-in and sign off (depending on discretionary budget)
Deploying/training operations staff can also take a little time. Its important that "on the ground staff" know that smartphone content is accepted and what they need to do when a customer presents their Pass to take a real world action. The more branches or stores you want the Pass to be accepted at, the more time it may take.