When it comes to what the handheld will pack inside of it, I really hope Nintendo gets over their worry of RAM prices, and pack a lot more into it than they've had a bad habit of putting into their prior handhelds and consoles. The fact that the DSi jumped up from 4MB to 16MB I take as a good sign for the future; perhaps it might not be unreasonable to hope for as much as 64-128MB of RAM, which would be plenty for almost all applications if they were written right.
Processor-wise, they don't really need as much improvement as many might think. After all, the PSP's 222MHz CPU has proven fine enough to get far more advanced games than the 400-600MHz CPUs found in smartphones. (granted, the PSP uses a MIPS-architecture design, being more capable per-clock than an ARM) However, the DS2 could perhaps do with a dedicated hardware GPU, rather than relying on the CPU.
[citation][nom]m-manla[/nom]Nintendo systems don't have long shelf lives anymore. They have a lot of sales in the beginning but always slow down. So they have to make a new system. I like the way Sony and Microsoft is doing. Longer life in between systems.[/citation]
Sony and Microsoft's consoles have had no longer life than Nintendo's; contrary to what has been claimed, the lifespan of a console has, up to this point, remained 4-6 years; claims that they've held out longer have been as fabricated as their power claims. (just for those interested, the actual combined CPU+GPU floating-point power of the Xbox 360 and PS3 are, respectively, 43.2 and 212 GFlops... Misleading figures that have little bearing on their capability for gaming, too)
Historically, a new generation of consoles has come around close to every 5th year; this pattern was started by Nintendo with the NES in 1985, followed by the SNES in 1991, the N64 in 1996, the Game Cube in 2001, and the Wii in 2006. Sega did the same, with the Master System in 1985, the Genesis in 1989, the Saturn in 1994, and the Dreamcast in 1999. Microsoft actually went a bit quick, as the Xbox came out in 2001, and was tossed aside by the 360 in 2005. Sony has followed suit as well; the PS1 came out in 1995, and the PS2 in 2000. The longest gap for them was 6 years for the PS3 in 2006, forgivable due to its wild success.
As far as handhelds go, the cycle seems to have gotten a little quicker, if we consider the DSi and DS two different handhelds; the Game Boy had a long shelf life from 1989 to 1998, when the Game Boy Color displaced it. Then the Game Boy Advance in 2001, the DS in 2004, and the DSi in 2008.