Nintendo could buy-out SE or other major publisher as they don't need to have a ton of disposable income to do it (which they have anyway), they'd finance it with the banks and likely some share swapping, etc. Nintendo is in an incredible financial position right now and would almost certainly be backed by banks and investors for any sane buyout.
The question is who is most in line with Nintendo's thinking, standards, and would add the most to the line-up? They might value a publisher who's strong in an area where they are weak, rather than a company like Sega who would be more of the same to a large degree. Western publishers are certainly on the table too, as they are weak in FPS, sandbox and sports games so a company like Bungie or R* might be seen as a desirable asset.











