The problem is that you can do it one of three ways right?
Straight historical game: Won't sell well internationally because it's viewed as "boring". Also, viking raids are not exactly good advertisement for the RPG industry what with all the murdering of random innocent people, raping and slavery.
You can of course do a bunch of cool stuff that isn't about that, I have in the past, but when you have to specifically make a Viking campaign NOT about going viking..it'd be like a game about the Foreign Legion and all you do is fill out paperwork
"Viking fantasy": What all the American companies making viking games do: Heavy metal album covers, big axes and some faux-nordic paint on a bog-standard D&D fantasy setup. I've made a formal vow to never buy one of these dreadful games again.
Fantasy game the way it ought to be done: Delve into whatever version of the mythology you prefer and create a game that feels like it takes place in the kind of world the norsemen thought they lived in. There's been some takes on this, but I don't think it has been done properly yet.
Ironically despite not actually being based on mythology, Trudvang feels that way to an extent, though the rules are a bit wonky.
A Nordic take on Maelstrom Domesday would be rather cool, for example.