Hi guys. One of the locals answering here located in the Reykjavik area. Been snowkiting/kitesurfing around here for the last 10 years. There aren't many of us here maybe a group of 5-8 active kiters.
Every year is different now maybe thanks to global warming, but to be sure don't come until January the very first although we kitesurf almost every day of the year and snow came early this year, about a month ago, but could just as easily wash away with a good rain session.
You could always hit the glaciers, like the one in the video which I recognize as Langjökull around 200km from Reykjavik. It's really the only one I've snowkited on a few times.
The fact is that we have conditions in the country on par with the best locations around the world I think if you travel a bit (minus the heat of course!). But we are lazy. We can go snowkiting only 30km from Reykjavik backcountry of the local skiing area and our beaches - well, we can go out in every wind direction on a wide empty sandy beach within a 15 min. drive. If it's longer than that it's TOO FAR. We're spoiled rotten.
You're right, north of the country at Tröllaskagi is a place we've been talking about visiting for ages. We've seen it and been there but never snowkiting. It's heaven. But for us it's a 500km drive, so.... (remember spoiled!). You might be right march/april even May might be a good time. But then again you never know, usually you will get good wind but could get unlucky. Later on in the wintertime the wind usually settles more, so no violent stuff if your not up for that. Than again be sure to bring all your gear, although we usually get away with 10-12m foils and a smaller storm kite (maybe 4-7m foil).
I'll let the guys know about the thread on our local group in Facebook. One of them has been organizing trips to Iceland/Langjökull glacier for some years now.
Just throw us some questions in here an we'll do our best