2 year headstart I think would be the way to go, developers would not be able to "shun" Nintendo in that case because they would simply have too large of an install base to ignore. 

Plus I would suggest an easy/cheap to upgrade console too, so that would prevent the urge to go buy a $400 PS5 if you can just upgrade your existing Nintendo console for $100-$200 or so. 

Maybe not the ideal solution, but the best one competitively for Nintendo. 

Besides I think when you get to a console that can generate like 5-6 TFLOPS of processing power, you really are starting to hit a point of diminishing returns beyond that because I don't think many devs will even be able to afford to make a game that pushes a 10+ TFLOP console to its maximum. 

Such a console should be able to generate graphics like this in real time:

I don't think it matters too much, but launching early has almost always been preferable. The key is that the system is desirable to either non-Nintendo core gamers or casual gamers or both. With their current state - and barring a Wii U turnaround - it has to be really thought out and can't be simply a new console release. My plan would be:
-Release an iPad mini sized tablet/handheld hybrid next year. Powerful and cool, it will eventually link to the new console. It's pushed hard to a wide audience. It will have a great ehop and virtual console and online games, but have a paid subscription service.
-Develop a powerful console at least 3-4X the PS4. Controllers work through wifi and the tablet can be a controller/second screen. Up to four tablets can link with the console. It will launch at a high price point with an online subscription, but be promoted as a premium product that even XBOne or PS4 owners would envy. Call it NES2 to trigger some nostalgia in older gamers and promote a back-to-basis approach.
-Buy or hire a couple solid devs to start the software now for the console's launch. There needs to be a key launch title in place for the core audience that builds hype: I would develop a massive game that implements the previously launched Tablet heavily to form a unique experience. My game would be something set in the Metroid universe, but all new in title and theme. Perhaps involving a group of 4 bounty hunters (one of which could be Samus, but the others just as important and unique) traveling back in time to recover an artifact and fighting a mix of aliens and dinosaurs. I would hype it by releasing 4 classic side-scroler adventures for the Tablet in advance, telling their back stories. Then the massive NES2 launch title would come out and be a 1st/3rd person 3D shooter with all four characters. Multiplayer could be played using tablets and the NES2 (or just the console) and competitive online multiplayer would be awesome.
-A second launch title would be a Wii Sports type title that would again incorporate multiple tablets. A unique version of games like pong could be played in a living room using motion-sensing tablets and an augmented reality through the screen. You would physically move the tablets and bounce balls back and forth and the overall action would be seen on the TV. This could possibly be a pack-in.
-Also ready for launch would be Super Mario Galaxy 3 (for some Wii generation nostalgia), Last Story 2 with online or Tablet based multiplayer, and a Shin'en developed F-Zero.
-Key 3rd parties like COD, GTA would be courted and possibly paid for ports.
-Traditional Nintendo franchises would follow as the price of the NES 2 was lowered over time and a more casual audience is targeted.

So this system could launch any time after Wii U has been on the market for 5 years. The key though, is that the system and its games are truly ready. If you don`t have several key, must-have groundbreaking titles ready, delay until you do. Simple as that.

How about A: announcing the release date and price of your console a little it earlier than a few weeks before it launches, and B: actually advertising the damn thing?

Oh and C: partnering with 3rd parties to promote your console as the flagship console for "insert AAA franchise here" the way both Sony and M$ do. Look at all the 3rd party game commercials that feature the 360/X1 or PS3/PS4 at the end... this is because both companies pay a little extra to promote their consoles alongside big releases. When was the last time you saw Nintendo actively promote a 3rd party game on their consoles? Never.

When you refuse to share the spotlight and make your console all about you, is it any wonder why 3rd parties don't want to deal with Nintendo?

They should choose a good name.

That's the first thing.

They should also release more shooting games such as Metorid.

shooting games are very popular.

Well definitely needs a rather large pile of new IP's that will appeal to adults. It's great that they have all of these family/casual friendly games (They ARE good games, to be sure). But they need some games with complex and mature story telling. If they could create say 2-5 big mature games, this would combine with their already stellar roster to make a console everyone wants!

This is of course assuming they get the other things right too like power, price, and features.

Nintendo will probably launch a new console in holiday 2017 which is 5 years after the WiiU's launch! They will also need to make sure the console is not too weak and that game droughts won't cause problems!

They already do lol.

Yeah, despite diminising returns in the actual end visual product, I think it will be surprising the graphical improvements and demands that will be around in 3 years or so.  If Nintendo really wants to capture the core market, they do need a product with some power well beyond current console levels.  If they switch to a paid online model, they could potentially do so and still have an affordable price - as Sony did with PS4.

Whenever they release thier next console they are going to need to invest a lot more capital on the front end than they are used to doing- they won t have much credibility re telling the market place what they will do- they will have to show the market place 1st - so they will have to have games ready for release, and some 3 rd parties locked in - which will all take a lot of money being invested before they sell the 1st console

2 year head start with a traditional gaming console.

Best way to beat MS and Sony is time. 1 year head start can't cut it, so do 2.