It WOULD have been nice. Microsoft's grand-unified platform included some good ideas, and potential for more, which would have benefited everyone. But they were so way way way late to the game. They needed to be pouring out product once Android started to stick, preferably sooner. Instead, their desperate catch-up strategy of leveraging Windows Desktop as a platform to sell Phone (looking at you, Windows 8) only angered the public... forcing live-tiles and "modern" apps on desktop users did NOT make them turn around and buy Phones, at least because it was part of a new, buggy, immature platform, where iOS and Android had had time to become reliable and ubiquitous.
Microsoft could try again in a few years, by making touch-friendly desktop and Surface really really great (somehow), along with really great iOS and Android tie-in apps, which get used so extensively that a market comes into existence for a phone more dedicated to those functions. Or, Microsoft could just "back in" to a new phone market by offering, over years and years, smaller and smaller Surfaces, with phone capabilities, but also with BlueTooth and HDMI ports that drive a desktop (in other words, a pocket-sized PC with Skype and a built-in touch-screen). This, of course, remains to be seen. iOS and Android are not going to wait for Microsoft to catch up. That's what happens when you miss the boat (looking at you, Steve Ballmer).