The only reason I have remained loyal to Nintendo to this point is becuase the quality has remained high. If quality slipped as a result of them going 3rd party I would be less likely to support Nintendo the way I do now. I would expect nothing short of their games being even better since they would be able to put them on more cutting edge hardware in terms of processing power.
Having said all of this I really don't expect Nintnedo to go 3rd party any time soon. Between Wiiu and 3ds I'm fully expecting Nintendo to sell 150 million units of hardware.