Not being able to charge for updates is a problem that affects almost every single paid app (assuming the app is supported across multiple versions and major updates) in all the app stores. This is an unsustainable proposition for most developers.
At a recent Seattle Xcoders meeting in Redmond, our speaker spoke about how he had given up his indie business and had now switched to contracting (disclosure: I run this meeting and had asked the speaker to speak).
At the meeting, I noted that Apple made its profits through hardware and they could therefore afford to make their software free. Similarly, Google is an ads company and so they don't need to charge for their software. However, the dominance of these companies means that most users/consumers expect all their software to be free (and the small minority that downloads paid apps wants upgrades to be free).
It is going to be an uphill battle for any "software" company to survive in the future. IMO that applies primarily to indie devs (I'm one myself) who sell apps in the app stores, but the problem also extends to large companies like Microsoft.