My recommendation is if you don't get one before the holidays (1520) you might as well wait until later on in 2015 for the implementation of Windows 10. Trust me the 1520 is an amazing piece of technology and you wouldn't be disappointed, but there's been a lot of chatter about new phones coming out especially around the launch of 10. I love my 1520, and as far as I'm concerned, I have my flagship.
I have waited a long time after 1520 but they didn't release any flagship after that, Windows 10 is going to be showed in next build which I think is going to be in next April, about 5 months ! and usually they will introduce new hardware after that !