If Pay Pal does not start to accept bitcoin, it is going to be defeated by incresing numbers of users of bitcoin. But at first, they need to a legal basis to implement it in certain countries.
The only useful implementation for Bitcoin and other crypto currencies is to have it function as an alternative option for users top up their balances. The rest isn't of importance to them.
PayPal transactions happen within their ecosystem which are instant already, which means that there is nothing to gain here. It's a service focusing on commercial payments offering buyers zero fee transactions.
If crypto becomes too dominant they could simply choose to lower their fees as a way to compete, and I'm sure it will work out for them. Another thing is that PayPal could easily launch its own PayPal dollar stablecoin.