Obviously you now need to add an API client layer but in terms of code organization, if your packages are cleanly separated then you've done a lot of the work already. (Transactions being the obvious piece that you'll often have to rethink when crossing a service boundary).
The advantage of this approach is that it's much easier to refactor your internal "services" when they are just packages, than it is to refactor microservices after you've extracted them and set them free (since upgrading microservice APIs requires more coordination and you can't upgrade clients and servers all in one go, as you often can inside the same codebase).
