I remember when Android was at 1.3% marketshare, and Apple was dominant. The conventional wisdom of the day was that there was no way that Android would ever take over the market, yet they did.
(And no, the Verizon "Droid" campaign had little to do with it -- the vast majority of Android sales are outside the USA, where Verizon isn't a significant player).
Never say "never."
That said, I expect that WP will be around 10% of the market. Some will support it, some won't. Those who won't will lose my business.
I have a significant amount of savings and investment with a bank that told me they have no plans for a WP app (though they support iOS to an extreme degree and Android to a limited degree). I told my "relationship manager" that I was thinking of moving to another bank, and she was stunned. I said "I want an app for Windows Phone 8, and Chase offers one while you don't. Please tell that to your senior people and get things moving. A bank branch costs over $1 million to open and staff. A decent mobile app costs $150K to build. Are you really going to tell millions of WP users that you don't want their business and send them to Chase or B of A?"
We'll see if it makes a difference. Windows Phone users may not be the biggest population out there, but we are 14 million strong, with incomes and needs of our own, and ignoring us completely means that some competitors will simply profit disproportionately from our business.