Yes, you can use Pay-Per-Return after the 50.  However, it the PPR fees are quite high, especially if you need the State too.  The last I checked, the "break even" point (if you need the State return too) is about 6-8 returns over the 50.  

For next year, if you are pretty sure you will go over the 50, consider the Unlimited.  Besides including 2 additional States, and you would have more returns available if you ever have late-filers in future years or if you need to amend a previous-year return for a new client.