This is for mobile phones and probably one day will do it for computers when all computers come equipped standard with mic.
Not likely. Voice recognition actually makes your account more vulnerable if someone really wants to target you. PLA did a very interesting experiment with Bell a while back demostrating its vulnerability:
Doubt it will ever be implemented on all users. As much as eBay/PayPal can suck. They know there are a ton of stealth'ers out there who do provide revenue to them if you play their rules. I don't see this ever being a hard requirement unless you have a very large volume account.