In a move to encourage upgrades to Windows Phone 7.5 Mango, the most recent version of this mobile OS, Microsoft will soon be preventing users from purchasing or upgrading apps unless their smartphone’s OS is up-to-date.
Giving no other timeframe other than “starting in the next few weeks,” a Windows Phone blog post spelled it all out, stating that “you’ll soon need Windows Phone 7.5 installed on your phone to buy and download new apps, or update existing ones.”
Users without Windows Phone 7.5 will still be able to browse the Marketplace, but upon attempting to install a new app or update one they already have, they will encounter an error message. In order to do upgrade to the most recent version of the OS, users must plug their phones into their computers and use Microsoft’s Zune desktop software to initiate the upgrade, as it cannot be done OTA.
This does not penalize users of older devices. An upgrade to version 7.5 is available for every model that was released running Windows Phone 7.
Speaking of the Zune software, also mentioned in the blog post was the fact that apps will no longer be available for purchase through the desktop client. Those looking to download apps will now only be able to do so through their phones or through the browser-based web Marketplace, which is accessible from internet-connected PCs and Macs.
Source: Windows Phone Blog