Sure, paypal is the big kid on the block right now, but who's to say they won't start accepting bitcoin as one of many international currencies?
Simple, their TOS forbids currency changing so you cant buy BTC using paypal on exchanges.
HOWEVER..this is a way around it, and if you work closely with paypal, you can get it done
Coming soon:
www.BitInstant.com - Providing Instant Transfer Services for the BitCoin Economy.
Instantly fund your exchange account with BitInstant using Paypal and Liberty Reserve