Whatever benefit we'd have from a Windows Phone today, it's laughable to think that Microsoft wouldn't be doubling down on exactly the sort of locked-down devices Apple (and now Google) have or are moving towards.
Their only vaguely "open" platform (Windows) is like that because of legacy compatibility and customers, but for anything new Microsoft always wanted to sell you an Xbox that could make phonecalls. Try writing and deploying an app on that without a developer account.