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Seriously? Have you ever tried setting up a payment solution for a business domiciled outside the US? PayPal is the ONLY viable online payment solution for businesses in many countries. While I wish there was some viable alternative, there isn't.
You also need to compare apples to apples. PayPal is an all-in-one payment solution. Braintree is NOT a payment solution, it's just a payment gateway. You'll need to get a merchant account to hook up to the payment gateway. THAT is the problem, as merchant accounts require large deposits and usually large transaction fees as well. But I can get started with PayPal right away.
Stripe is a all-in-one payment solution. However, they aren't international and is only available to US merchants. I would be the first to sign up if they went international but this hasn't happened yet.
So no, PayPal isn't going away just yet.
2 years ago on Exactly How Screwed Is PayPal? (Hint: Very)