Joe Belfiore in a series of tweets has also talked about the “internal testing going on” and “not all devices will get the first Window 10 for Phones preview.
Hey all: we ARE working on Win10 for 512MB, including 520. Our ambition is to make #Win10 available for these devices but features may vary
— joebelfiore (@joebelfiore) February 8, 2015
Timing for various phones may be variable as well. When we first launch insider program, it’ll be a subset of phones with more coming latr
— joebelfiore (@joebelfiore) February 8, 2015
Also, we’re on track for Insider build coming “in Feb” as Terry said at our 1/21 event. We need to complete internal testing 1st, hang in!
— joebelfiore (@joebelfiore) February 8, 2015