More than 1.5 million Windows Phone users have upgraded to WP8.1, as the Nokia Lumia 520 runs out of steam

AdDuplex has reported their monthly stats on the Windows Phone ecosystem as of April 17th 2014.

The biggest news is that, for the first time, the Nokia Lumia 520 has stopped growing, dropping from 34.5% to 34.3% of the Windows Phone market.

The Nokia Lumia 920 has made somewhat of a comeback, moving from 3rd to second place.

While AdDuplex does not put any major interpretation on the data, we could be seeing the effect of the rumours and announcement of the Nokia Lumia 630 and Nokia X.

Possibly more interesting, until we see the official Nokia sales figures for the quarter (which may be never), is the number of users who took the opportunity to upgrade to Windows Phone 8.1 via the Developer preview.

The stats reveal 3.1% of Windows Phone users have upgraded, which is around 1.5 million users if we assume 50 million Windows Phone users in the wild.

This likely represents the size of the power user segment of the market, which is an indication of how far Windows Phone has spread into the main stream, likely on the power of the cheap Nokia Lumia 520.

They also report on 4 new handsets, the Nokia RM-1010, RM1020 and RM-1027, with 480×854 screens, and RM-1045, the a 1080p 5” inch screen, which they assume is a code name for the Nokia Lumia 930.

AdDuplex will release their full stats tomorrow.