Considering the amount of utter hatred a lot of Bitcoin users have for Paypal I don't think the scenario will play out as you imagine and lets not forget that Bitcoin is open source and there are plenty of altcoins out there, I personally think software like Open Bazaar is going to be used more for trading in Bitcoin than Paypal/Ebay and those bastards at Paypal have been boasting and dragging their feet about Bitcoin adoption for months which makes me think they're going to do a shitty job implementing it.
Oh, did I also mention that they're trying to partner with GoCoin which has Brock Pierce in it's staff? Yeah, things are going to go really well for them, it's going to be fun to watch.
You think they just decided to implement BTC at PayPal recently? Dragging their feet is not my impression of how a company who specialises in payment processing approaches these matters. They didn't cave in to pressure. Now they're going to see first hand how to tweak BTC to their own ends. Oh it won't be called Bitcoin, but to think PayPal or even Apple turning around is from the minuscule amount of money they're losing in the big picture...
You know how Google, Apple, Microsoft etc made it big? Not by letting the little guy win. If PayPal becomes the de facto cryptocurrency service provider then who's to say they'll implement updated BTC protocol? Maybe they'll find mining too expensive when it can be secured for less money. You know, business.
It's going to be fun to watch only in the same way the weddings from Game of Thrones was fun to watch; the outcome was a massacre. Just not for the little guy.