Nintendo could try an excuse like that for years and no one would buy it.
DS was presented as a 3rd pillar, not as a successor to DS - as Wii U is being presented as a successor. That`s why i don`t really understand the DS reference.
Now, wouldn`t it be funny if Nintendo presented a Nintendo tablet as a 3rd pillar? Especially designed to appeal to that market while making it work together with Wii U and 3DS - and follow-up? The tablet would allow to play all games bought on 3DS and Wii U without buying a new copy and still work as a regular tablet.
I too can make wild predictions!