@ samboy2005,
OPNP website explicitly says that it is applicant's responsibility to maintain legal status in Canada during processing. So if you will not receive your nomination before PGWP expires the only option would be to leave Canada and wait for decision outside the country.
If you do receive your nomination sometime before PGWP expires, then you will have the following options:
1. Apply for WP right away, with support letter provided with nomination. (At max you can get 18 months extension)
2. With nomination apply to CIC, get the file # and only after that apply for bridge WP. ( At max you can get 12 months extension)
My advice would be call to OPNP and hurry them up (they usually understand such situations) and then call to CIC to clarify about implied status in your case.