ps4/vita are "like brothers" in the way they are describing things. iwata specifically cited apple's approach and even with apple, apps have seperate releases between iphone and ipad. it will be relatively easy to port back and forth but it still won't be effortless.
this is important because of 3rd parties, if they have to add even a little bit of extra effort they won't be happy. having to create 1.2 games instead of 1 to support both sides of this unified platform is 20% too much effort.
so if they don't garner 3rd parties than it's up to nintendo. even with all of nintendo on this one unified platform i still don't think they can make enough game to be viewed as relavant.
throw on top of that, sony is launching ps now soon and MS is strongly rumored to have their own service. years from now that will be a decent chunck of the gaming market. by no means 100% but even if it ~30% that's 30% of the market nintendo isn't getting. they will be, once again, a generation behind the competition.
i don't know who is going to win gen 9,... but if this is nintendo's approach i'd say they are out of the running.
This should answer your question.
Corporate Policy Meeting for Fiscal Year ending March 2013 (Posted last year, January 2013)
As you might already know from some newspaper reports, we will reorganize our development divisions next month for the first time in nine years. Two divisions which have independently developed handheld devices and home consoles will be united to form the Integrated Research & Development Division, which will be headed by Genyo Takeda, Senior Managing Director.
Last year we also started a project to integrate the architecture for our future platforms. What we mean by integrating platforms is not integrating handhelds devices and home consoles to make only one machine. What we are aiming at is to integrate the architecture to form a common basis for software development so that we can make software assets more transferrable, and operating systems and their build-in applications more portable, regardless of form factor or performance of each platform. They will also work to avoid software lineup shortages or software development delays which tend to happen just after the launch of new hardware.
Some time ago it was technologically impossible to have the same architecture for handheld devices and home consoles and what we did was therefore reasonable. Although it has not been long since we began to integrate the architecture and this will have no short-term result, we believe that it will provide a great benefit to our platform business in the long run. I am covering this topic as today is our Corporate Management Policy Briefing.
So basically a unified developer API and a unified OS with scalability built-in.