According to an unconfirmed report, Windows Phone 8 is going to come with hardware requirements that will prevent any current Windows Phone 7.5 model from running it.
Microsoft requires any device running Windows Phone 7.5 to have a single-core CPU and a WVGA (800 x 480) screen resolution. Windows Phone 8, dubbed Apollo, is reported to require a dual-core processor and a higher screen resolution. If this stays true, then none of today’s Windows Phones would be capable of running Apollo, which would cause a massive headache for customers who may have just bought a newly released Windows Phone like the Nokia Lumia 900 only to discover that it’s already obsolete.
At the Mobile World Conference in Barcelona, reporters from The Unwired noted that none of the major Windows Phone OEMs, with the exception of Nokia, announced a new Windows Phone running the very latest iteration of Windows Phone 7.5 (Tango). They speculate that these companies are holding off until Apollo so that their devices can be future-proof.
Keep in mind that these are all from unconfirmed reports and that Microsoft may end up allowing current devices to upgrade to Windows Phone 8.
Apollo is rumored to be released in Q4 2012. To read more about the Windows Phone 8 leaked features, check out a preview of it.