That would be a huge file, Scott. My Canon 5D Mark III, with a similar pixel count, turns out RAW files in the 50-60 MB range, so more than an order of magnitude smaller.
I know that there's a menu in Photoshop, I think it's the save menu, that gives some memory number. I'm not sure, but I think that's some loosey-goosey number representing how much operating RAM is needed to work with that image.