Gameboy had three'ish generations: Original (The Brick), Pocket, and Color.
Gameboy Advance had three generations: Original (DS Phat), SP, and Micro.
The DS has two generations: Original, and Lite.
What's missing in the above trends? A 3rd DS! Nintendo realized this problem, and solved it by announcing the DSi. If you read Japanese, you can look at their announcement page directly, otherwise, you can read about it on DS Fanboy. Kotaku has a nice comparison of the DSi/DS Lite. Here are its new features, and why they are mostly pointless.
We have enough cameras in our lives already! We have digital cameras, and our cell phones have cameras. On top of this, we've already had this before; remember the Game Boy Camera?
In case you don't remember it, it took crappy black/white pictures, and you could half-ass'ly edit them with such great tools as stamps and frames. What else could you do? You could print them with the Game Boy Printer
How will this be improved upon? It will take crappy color pictures, and you'll be able to edit them with your stylus. Improved? Yes. Still pointless and will get old real fast? Yes. But wait, there's two cameras! Sigh... Sure, games will try and implement this in some gimmicky fashion.
Implementing a DS feature in a gimmicky fashion? That sounds a lot like the microphone... Example uses: blowing out a candle in Phantom Hourglass, unsuccessfully screaming blue in Brain Age, objecting in Phoenix Wright, and making a fool out of yourself while playing games on the subway.
We have enough music players in our lives already! We have MP3 players, portable CD players, and our cell phones have them too.
Do we need SD storage? Not really, especially if they're also announcing that there will be internal storage. As long as we are still using cartridges, and not discs, there's no need. Sure, we need to store our music and pictures, but we don't need those at all. Sure, people use their PSPs as media players, but that's because they're also being used as video players, and can browse the internet. This leads us into...
The DS Lite had a version of Opera you could buy, and it wasn't good. The trend with computer screens is higher and higher resolutions, and websites follow suit. The DS just doesn't have a high enough resolution to do this effectively. This works somewhat on the PSP because of the higher resolution, but still not that well.
People (including myself) use the internet on their phones, so maybe this will be useful after all, but I'm remaining very skeptical.
My ranting ends here, this is a feature I fully support. I love XBLA, and although I don't actually use the WiiWare, I do like the idea of it. The VC... it's okay I guess. Will this be like the VC and just be Nintendo regurgitating a bunch of old games for more money? Yes, of course. If they do this like Wiiware/XBLA, and they do it well, this could be really great.
The Rest in Brief:
Smaller system: A smaller system and a brighter screen are my reasons for buying a DS Lite (note: not an upgrade from the DS Phat, it was my first purchase), and if they're going to make an upgrade, they have to do this, it's the way of technology. Thankfully they didn't take this as far as they did with the Micro, which became so small it was uncomfortable to hold.
Bigger screens: I approve.
Matte colors: Goodbye fingerprints. Not a big deal to me one way or the other.
Shorter battery life: Ouch; stupid decision.
Goodbye GBA support: I never play GBA games, but still seems like a bad call.
What it should look like.
I'm probably being a bit harsh here; it's not a new system, it's just an improvement, like all of the later systems in a series. It's hard to explain, but it feels as if Nintendo is just trying too hard, and throwing useless gimmicks at us. I would have rather had them just decrease the system size, increase the screen size, maybe increase the battery life, and drop the price instead of spending the extra money on worthless features.
: You could argue that the Game Boy Color wasn't really in the same generation, since it sort of had its own games, but I don't like this argument, and refuse to count it as its own system.