Nintendo is trying to get profitable again, killing off their biggest moneymaker and instead making further losses due to a new system launch is really a very contradicting move. We know that a big part of their loss in 2011 was due to their push to build a 3DS userbase. Right now they have a system that is beeing sold at a profit with a userbase that supports good software sales, 3DS basically dominates the software charts in a regular basis in Japan. And has a userbase that can generate million-sellers, the most the recent million seller beeing Puzzle & Dragons and Yokai-Watch with the potential to become one as well.
Sales aren´t as good as last year so far but still healthy, with options like new colours, price-cuts and a revision in combination with big sellers beeing the most reasonable ways to reignite sales, these are measures that they will take before they even consider a successor. Their priority is to be profitable and software sales by taking advantage of the soon bigger than PS2 userbase in Japan are the best way to achieve this.