Should I buy a 3ds or wait?

No you're safe. They won't even consider making a new one for 2 years. I know this because I searched it up when I wasnt sure if I wanted one.

Reasons:

1) because the Wii U comes out in about a year and games such as SSB use the 3DS in some way or anyother.

2) After the Wii U they would have to wait at least a year after the Wii U comes out, because everyone will want to get a 3DS and you'll have to give those people a chance tI play with it before they got bored of it.

... If that makes sense. XD

I doubt they'll make a slim design soon. The big N said so themselves. The 3DS has everything so tightly fitted in. The original DS had some space, so they eventually made a lite version. Unless they make super tiny hardware, then there might be a chance.

I just went ahead and bought mine.

Knowing Nintendo they will probably come up with a new redesigned 3DS, with better battery and smaller size just like DS lite. I'm waiting because of the same reason too, so yeah, you should wait.