Then why was the PS4 jump so damn tiny?

To specifically answer your question, in 2018 when Nintendo's next console comes out (which I am 100% sure will not have Wii in its name), but it will officialy start in 2017 with the Nintendo handheld

Nintendo handheld: 2016 or 2017
Nintendo home console: 2017 or 2018
Sony home console: between 2018 and 2020
MS home console: after Sony to make sure that they're more powerful. Or maybe a service for different devices
Sony handheld: never

I'm thinking 2017 with Nintendo's joint release of it's new handheld and home-console.

Then Sony and Microsoft's home-consoles the year after in 2018, though I could see Sony trying to ride the PS4 for as long as it can and wait to release a new system until as late as 2019, two years after the first combatant entered the 9th gen.

I think this will be a 5 or 6 year generation. Maybe less.
Backwards compatibility is a no brainer for next gen, which won't be difficult.

2020. Few things to note/consider.

All 3 manufacturers will release in the exact same year. Nintendo doesn't have the mindshare or brand power anymore to ell based on hype alone or from releasing first. If Nintendo comes a year early like they did this gen, no matter what they do, everyone will just assume that sony and Ms will do better and wait it out regardless. So nintendo has to come at the same time with everyone else and it least have hardware that is on par if not better than them.

We are no longer in the 5yr cycle. HD games simply cost too much and takes too long to make. That means that at best most studios would have 2-3 games released in a 7yr cycle. If we take into account that more money is made from game sales in relation to the market size, then the best time for any studio to be making games is in the 4th year and up of a console cycle. With the cost of HD gaming, devs/publishers will be less willing to jump start a new generation. Its a money thing.

The power argument, is completely irrelevant in the eys of publishers or devs. Are the consoles capable of 1080p/60, 1080p/30, 900p/60, 900p/30...etc. Yes they are. And as far as mass market appeal is concerned, especially when you consider that probably over 90% of everyone using a console has it hooked up to a display that peaks at 1080p or less; thats all that matters. We can talk about how GTA6 can or could look 5 times better on PCs from now till the sun burns out, it wouldn't stop it from selling over 30M copies on consoles. At the end of the day, thats all that matters to publishers. The sooner some gamers realize this the better. And once you get this, you will see that power and consoles never really go hand in hand.

I believe that the 3ds is the last traditional nintendo handheld we see. Their just isn't a market for a traditional handheld anymore. Next nintendo handheld (if they make one) will be a tablet/phone or maybe even both.

Sony & MS will go for 2018/19.

Nintendo has to release sooner because Wii U isn't making enough money to sustain their size, so 2016/17 for Wii U's successor.

because the PS3 was $800 to manufacture when it released lol and the PS4 is a big jump and low cost.  Everything is smoother and faster and devs are JUST getting used to it.  Hell I'm playing LoUR and it looks incredible compared to the PS3 version I can't even play it capped at 30 anymore.

The major hurdles to new hardware coming out is going to be the development tools. To effectively use another generation of hardware developers will need some quite advanced proceedural generation tools, which will automate creating the high texture graphics and functional levels we expect from a next gen game, but created automatically with some human tweaking.

I expect that will come together quickly once the pieces for it are available, and once that happens all the console manufacturers will leap on it to build a new console. Predicting when we'll hit that spot, though, is really hard.

I expect that Nintendo will completely reinvent itself come 2017 or 2018. Microsoft will quit trying to save the X1 shortly thereafter, and Sony will quit with the PS4 when they know what they're doing after it, whenever that happens to be.

To be honest, if the AAA game market collapses (and with Destiny costing $500 million, that looks to happen quite soon, now) I can see the market going the cheap or indy title route and graphics stabilizing for the better part of a decade. Why push graphics when you won't get your money back on it? Why upgrade the consoles when only a few PC developers needs the extra power. Heck, Crytek was going to complain about power, no matter what you gave them.

It's possible this gen could end as early as 2017, but it could also go on until 2028 if the market collapsed around it. My money is on 2020.