Nintendo could alleviate the Wii U's issues by simply upping the ante of their game development and hitting their core audience with quality titles. As for the 3DS successor, that system is not going anywhere for atleast two years. The Wii U and 3DS successors must be revealed at the same time. Nintendo is trying to close the gap between home console and handheld and the best time to that is right now with the 3DS and Wii U so that the infrastructure exists in the future. They need to get the universal system account going sooner rather than later.
Ideally they would announce both end of 2015 and launch them both in 2016.
but upping the ante of their game development? I'm not sure what that means. Did you mean upping the amount of their games in development? or raising the stakes on the types of games they develop (genres & IPs)?
Boosting production at this late stage in the game wouldn't bear fruit till maybe 2 years from now.
changing the types of games they are making would probably take just as long if not longer.
But if they got started now, the successor systems should have an awesome launch.
There is no doubt that Nintendo has accelerated their plans for their next consoles. However, it would cost them too much money to replace what they have right now. As for Nintendo upping the ante in their games, Nintendo needs to bring back all of their dormant franchises to the Wii U, which would include Metroid. The systems needs games and with the new Call of Duty looking less likely for the Wii U they need a hell of lot more than what they are churning out now, and no casual title is going to push systems.
Nintendo could build bridges for their next systems by extending olive branches in the present. They could money hat Rockstar to make a remake of Max Payne that is exclusive to the Wii U. Or they could do a Spec Ops sequel for the Wii U. They could bribe Metal Gear Reveangance 2 onto the Wii U. The potential is limitless and with the industry as cash strapped as it is having a five billion dollar war chest is a blessing one could use to their advantage.