I think the bigger issue here is that the fact that these shortcomings of the store exist in the first place is kind of a huge red flag that Microsoft doesn't really know what they're doing.
Even going beyond gaming, the Windows store is an absolute mess of malware and fake apps with absolutely zero quality control. It's like if a restaurant opened and sold expired food and then pledged they'd get that sorted out by the end of the year. That's kind of too little, too late, when your competitors already have a proper handle on the basics you're struggling with. And unified code bases for multiple platforms is already a solved problem which goes well beyond just "Windows" devices. I'm not really seeing what this brings to the table that isn't already doable, and on far more devices, like all those indie games that have versions for Windows, Mac, Linux, Xbox, PS4, PS3 and PSVita. This just reeks of smoke with the only "benefit" being that Microsoft will now theoretically get a 20% cut or whatever of Windows apps sold, which is more than the 0% it currently is (and, it should be noted, the fact that they were a free-for-all to code for is exactly why Microsoft grew so big and powerful in the first place, when all of its competitors were locked ecosystems).
And you really shouldn't take anything Microsoft promises for the future at face value (or any large company/politician/whatever), Microsoft especially has a history of not delivering on its promises. They were saying all Xbox Ones would be dev kits three years ago (since before the console's release) and that has yet to happen. They promised it would happen "this year" in 2014, and again in 2015. It's now neither of those years.