If Sony is willing to offer Nintendo a PARTNERSHIP (note: I said partnership, not a "come here and be 2nd party nobody for us") I think Nintendo would strongly consider it at this point. Sony is a Japanese company with a president who comes from a game division and they are not big enough to buy out Nintendo (so Nintendo maintains independence).
Honestly I think all of those factors are attractive to Nintendo.
Sony wants to be in handheld gaming but its clear as day they don't know what they're doing there.
Nintendo wants to sell console software but have had a very difficult go of it really for 12/13 of the last 16 years as they've been forced to accept a no.2/3 position in the market most of the time.
They just to me seem like a perfect fit because they would complement each other in areas where the other is weakest.
