As market share goes up, so will the demand for apps. The latest version of Windows Phone isn't even officially a year old yet. I think they've done a respectable job at gaining market share and building out the platform. If they can steadily continue to climb the developers will follow.
The 1520 looks really tempting to me. The size is a bit intimidating though. I have a Lumia 920 and iPhone. Took some time for me to get used to the size of the 920. Can't imagine how the 1520 will feel. Imagine if they put the 41MP camera in that bad boy. This thing would be a beast.
I think 1520 will feature a 20mp camera. Still better than our Lumia 920 :) The lens will probably be the same again as it is more important than the MP feature.
I truly want to get a 1520 and I don't mind the size but how I am going to carry it around me I don't know.