The collaboration with DeNA has nothing to do with investors or pressure to build mobile apps.
Iwata: Nintendo Wasn't Pushed Into Developing For Mobile : Read more
Iwata: Nintendo Wasn't Pushed Into Developing For Mobile : Read more
Given the stubborness of Nintendo to adapt to anything I can believe that the decision was made on their own terms but with mobile being so prevalent I do feel they felt some pressure to head in that direction.
Still the best place to play nintendo (and the only place) is on nintendo ...atleast until you get an emulator working.
I have a feeling that these will be more "companion" games more than anything else for now. Though I think pokemon would do huge in the mobile market . in app purchases for more pokemon storage and such.