A Reddit user and Microsoft employee who goes by the the name BAADFOOD on Reddit, has spilled beans on timings of next major Windows Phone upgrade, which according to him can come as Windows Phone 8.2 or Windows Phone 9. According to details revealed Windows Phone users can expect a major update like Window Phone 8.1 every 6-8 months and a big release every 12-24 months.
It is not only about Windows Phone though and even Xbox and Windows will get releases with updates with new features every 6-8 months. In reply to a question he clarifies that he is talking about major updates like Windows Phone 8.1 coming every 6-8 months and not GDR updates. 
He also confirms upcoming Windows Phone 8.2 or Windows Phone 9 to be a major upgrade over Windows Phone 8.1.
Source: Reddit
