I still think it's possible, if Paypal uses bitcoin as a mode of payment on top of visa/debit/echeck, they can charge the same fees they already do, Ebay charges a fee as well for selling, they would not lose out, the credit card companies may though if they do that..
Definitely not. The main advantage Bitcoin have over Paypal is the low fees and currency exchange charges. If we give away those advantages, then the attractiveness of Bitcoin will diminish.