I would really like to wait and see how this plays out -- the proposal I'm working on is careful not to have any effect at runtime (as long as the typing.py module can be imported and as long as the annotation expressions don't raise exceptions), and use of a static checker is entirely optional and voluntary.
Perhaps the PEP should define some way to tell the type checker not to follow certain imports? That would be useful in case you have a program that tries to follow the annotation conventions for static checking but imports some library that uses annotations for a different purpose. You can probably do this already for mypy by writing a stub module.