Im starting to think Nintendo will wait to see what Smash does for the system, and if they're not satisfied with the results in 6mos, I think they will "delay" Zelda and have it ready for the next gen Fusion (lmultiple hw types & same game = no more "double dipping").  

Nintendo is in the business of selling lots of games, and you need a big install base to really profit (i.e. NSMB wii and MKWii).  Nintendo was on record as not happy with  gamecube and even called it a failure.  They can't afford to waste efforts on a system no one cares for.  I am betting on the next Zelda becoming a multiplat.

Nintendo is at a very low point right now, humiliated and lapped by the competition despite being available on the market for a year longer.  PS4 is about to double Wii u soon in ltd. So the bottom line is Nintendo and major 3rd parties are done, and they have to support themselves to boast a rich/diverse game library, under a unified system.  What throws a wrench in this plan is the new 3DS, which extends the life of that console.  But I think there's a decent chance of an announcement at E3 '16 for a winter '16 release of the Fusion HH.  Home console or FusioNES will be made avail. in spring '17.

I'd give it top 1 more year, maybe 2 before Nintendo releases a proper "next-gen" console...

The question is, will they make it third party friendly enough?

What will be the gimmick this time? (I hope it's just a nice controller with decent specs on the console)

New 3DS is nothing special. It's the traditional "last gasp revision" that Nintendo did for both the GBA and DS. 

In fact it's timing hints strongly at a new Nintendo portable in 2016. 

The third and final revision of the DS was the DSi XL which launched in March 2010 in North America. The 3DS (the next-gen successor) launched in April 2011, 13 months later. 

I called a new Nintendo handheld revision this fall a while back, if they wanted to get one more model in before a 2016 Fusion launch they'd be launching it ... right as they are ... right on cue. Virtually the same schedule as the DS -- 3DS transition.

Keep in mind too that 3DS will still need to be stocked for years even after a hypothetical Fusion platform comes out. It will be the cheapo/budget option for parents, especially for kids who just want to get into the amiibo ecosystem. 

Wow, you're completely off the mark with that one XD