I would say never.
Ebay bought Paypal to earn more, solve fraud cases faster and control users.
Bitcoin would increase fraud cases, overwhelm the control of users and in the longterm if they start to accept bitcoin and promote it bitcoin would win and leave the paypal behind begging for some users.

If paypal was not bought by ebay , maybe ebay would add bitcoin, but right now they are afraid that if they integrate bitcoin more people will realise that they don't need paypal.

Their goal is to control and rip the profit with crazy taxes

They can't realise these goals with Bitcoin