This would be just stupid thign to do, in 2009 PS3 will have one of best gaming years. =)
It was GREAT in 2008, it will be even better in 2009 for PS3:
KillZone 2
Yakuza 3
Heavy Rain
Gran Turismo 5
God of War 3
InFamous
Uncharted 2
Quantum Theory
Final Fantasy XIII
White Knight Chronicles
Demon`s Soul
Final Fantasy XIII:versus
MAG
Agency
Ico 3
Wardevil
EyePet
These are only KNOWN exclusives, there much more to be announced.
And NO, Wii is not hitting exclusive line, 3rd parties still HIGHLY support PS360.
Anyway, do whatever you want, you will still have to buy PS3 later, since it`s only 2 years on the market, and it still atleast 5 years for it to go.
And there are so MANY exclusive PS3 games for 2009, and MUCH more unknown for other 4-5 years.
Unless you are not interested in what PS3 can offer.
In the end only you will regret selling PS3. =)
But, yes, you should get DSi, when it`s possible.
Every 5 seconds on earth one child dies from hunger...
2009.04.30 - PS3 will OUTSELL x360 atleast by the middle of 2010. Japan+Europe > NA.


Gran Turismo 3 - 1,06 mln. in 3 weeks with around 4 mln. PS2 on the launch.
Gran Turismo 4 - 1,16 mln. with 18 mln. PS2 on the launch.
Final Fantasy X - around 2 mln. with 5 mln. PS2 on the launch.
Final Fantasy X-2 - 2.4 mln. with 12 mln. PS2 on the launch.
1.8 mln. PS3 today(2008.01.17) in Japan. Now(2009.04.30) 3.16 mln. PS3 were sold in Japan.
PS3 will reach 4 mln. in Japan by the end of 2009 with average weekly sales 25k.
PS3 may reach 5 mln. in Japan by the end of 2009 with average weekly sales 50k.
PS2 2001 vs PS3 2008 sales numbers =) + New games released in Japan by 2009 that passed 100k so far