The main argument for buying consoles is their convenience, not longevity.
That's besides the point though - you have to take into account the fact that Nintendo has a long-term strategy of using "tried and true" components in their handhelds which leads to them being really on the "low-end" side of the specs spectrum, and there's only so much you can do on weak hardware.
Yes, their handhelds used to have much longer life cycles, (the original Game Boy can be an example here), but today mobile tech moves forwards at a much, much faster rate - faster than ever, in fact. Within a few years we went from single-core sub-1GHz mobile CPU's to octacore ones nearing 2GHz with embedded GPU's - it's hard to keep up in this race.
That, and the 3DS isn't going anywhere. It's not being phased out, we've established that already.
Consoles, home and handheld, are not "tech". They are already obsolete at the time of their release and are walled gardens with limited functionality. That has been ALWAYS the case, since the original NES which was way underpowered for its time...
If one needs to keep buying new underpowered and obsolete hardware every few years just to play a couple of exclusive games, might as well buy pcs and android tablets with game buttons like the archos gamepad 2 (google it, i have one and it is fantastic for android games and emulators...).
You know how much this Archos Gamepad 2 cost me? 120 euros. The original 3ds is around 150 here in my country.... Want to compare specs?
The tablet has 4xA9 (75% faster clock for clock than the arm 11 the 3ds uses) 1.6ghz cores(instead of 2x268mhz), 2gb ram instead of 128mb, and a 20gflops gpu instead of a mere 5 gflops for the 3ds.... With a 800p screen, all touch. Not to mention the battery life, 10 hours of gaming...
And i can use that device for everything, internet, email, videos, music, gaming, ebook reading, you name it. And the games are almost Vita quality in the graphical department... Plus it came with two graphical advanced games preinstalled for free, modern combat 4 and asphalt 8...
I don't want to advertise this device, i just want a comparison to be made for the sake of argument.
So tell me, are a couple of Nintendo exclusives like Super Mario 3D land, pokemon and zelda, enough to pay much more for a weaker device every few years?
When you buy a console and games for it, then what you are really buying is access to its games. And the cost of the hardware is just an up front cost which should be added on the cost of games.
Here in my country, most AAA 3ds games cost 40-50 euros and stay there since Nintendo... And let's say the 3ds costs 180 euros (that's how much i paid 3 years ago after the price reduction). If i would like to buy 5 games for it, and each game costs 40, then the real cost of the game is 76 euros, if you add the cost of the hardware on top of it. After all, i paid 180+5x40=380 for 5 games...There is nothing else i can to on the thing. The internet and the other apps are a joke...
So are Nintendo games worth 76 euros each?
While on Android, you can get an almost exact port of the Xcom from ps3 for less than 10 euros... Most games are way cheaper than that, and you are not losing access to them when you upgrade to a new device...
I like Nintendo games, i really do, but they are not worth that much. Especially if they shorten the life cycles and hence double the amount of hardware spent on them for half the must have exclusives...
Most japanese companies like Squareenix are already porting their games on android. So with each year, spending on a dedicated handheld is a losing proposition.
The only way Nintendo's consoles would be worthwile would be if they supported their consoles for longer, in order to cut hardware costs, plus making their software a little cheaper... For example 60 euros to preorder Pokemon remakes for the 3ds is INSANE. Those games do not cost that much to make...
By asking too much from the consumer, Nintendo is destroying the very business segment that sustains it...