In another thread(which I can't remember) someone mentioned an author that has written several successful steampunk novels. It's these type of authors that a rpg company needs to contact and come to some arrangement to use their IP.
Cherie Priest. While it would be nice to get her to officially back a supplement or setting it really wouldn't be necessary. Steampunk is widely accepted as a certain time frame in real world earth with a sci-fi element thrown in. It's modern day Jules Vern essentially. So long as you aren't blatantly taking from the various works out there there's really no worries in regards to rights.
I still think that Steampunk is just asking for a good RPG.
Are you saying that RM is that game? If so, the only way this is going to happen is if someone steps up to mark and writes it. But as Nicholas has mention recently, writers flake out and nothing happens, which is unfortunately so true of a lot of people these days I've found. To be honest I just can't see it happening as I also would like to see/work on a Steampunk genre if the call was made.
Well the fact that writers flake out is obviously no reason to give up... if it was RM would have pretty much died completely long ago. They really HAVE to rely on freelancers now and, for the most part, did before once the core-books were out. ANY RPG could make a good Steampunk setting or at least a source book that fits it into that RPGs framework. Considering the relative popularity of Steampunk I think it could potentially put a game system on the map (or BACK on the map) if done well.
I've got several ideas for books that I'd likely propose, but I need to be comfortable with my potential to have the free time to complete them in a timely manner. Currently I don't think I'm at that point. I could do it, but I'd be locking myself away from friends/family for a few months and I'm not going to do that now (especially when we actually have NICE weather here in the Seattle area!)