I got this (and several others like it) last week:
hi my name is Lindsay and love love your books and i was wondering if you're going to make a 4th Aud Torvingen book
My answer is always the same: I'll never say never. And I have books 4 and 5 plotted out in my head. I know exactly what happens next. (Aud takes a while to adjust to married life...)
But right now I'm working on an entirely different project, one that will occupy me for years. It's a triptych of novels about Hild of Whitby*--a seventh century girl from the north of Britain who grew up to change the world. The first book covers her life from birth to her wedding (not that they actually had weddings the way we understand it). The second follows her during her marriage, the tragedy that ensues, and her agreement to run an abbey (ditto). The third recounts her time as an abbess and counsellor to kings, right up to her death in 680.
All three books will be full of epicness: the rise and fall of kingdoms, wars, plague, the time of conversion and nation-building, the change from a heroic society to a Christian one. Not to mention, sex and love, drama and loneliness, peace and belonging.
So, no, no Aud for a while. Though, if it helps, you could think of the Hild novel I'm writing as an Aud book, just set when she was a child, and in a past life...