I enjoy "What If?" questions, so I will jump on this and see where it goes:
Nintendo, the day they shut down (God-forbid), will, over a period of a year or so, will leave a huge void in the gaming market (there would be a period of a couple of months where stores and retailers will still be selling what's left of the Nintendo products that were most currently released). After a year, there would be a huge, yet subtle, impact left upon the gaming industry in the form of dwindling innovative games. Face it: innovative console games are mostly found on Nintendo systems, especially in the past few years becuse innovation costs money and a lot of people don't want to make such a risky investment on something that could fail. If there is anything that Nintendo is known for, it is for their unique, innovative concepts that ultimately get replicated by everyone else. And since Nintendo has the funds and, more importantly, the willingness to go all out for a brand new gaming concept or genre, the death of Nintendo means a very fast decline in unique and innovative games. The PC-gaming market would be the breeding grounds for the majority of new and, as a result, best-selling games because big-name players like Sony and Microsoft were always shaky and sceptical of new ideas and innovative concepts...
But do I worry? Nah, not when hardcore gamers like myself intend on funding Nintendo later in life once I start a successful business company (after one or two failures, of course!)! My loyalty is that strong because Nintendo has affected my life so much.