1) $179
Nintendo does have some capacity to increase the price of the 3DS, but I believe it will remain in the $149 to $199 range; and $179 seems entirely reasonable.
2) No
The DSLite is about as large as a console can get and still fit in most men’s pockets and most women’s purses. While I wouldn’t bet on Nintendo releasing a dramatically smaller console than the DSLite I would think that they would be more inclined to shrink it (if they can) than to produce a larger console.
3) Probably not
I wouldn’t expect the functionality to implement 3D on the 3DS would be available to a Nintendo DS game; and this would mean that the target platform would have to switch to the 3DS for them to target this functionality. I do admit that there is a slight possibility that 3D Nintendo DS games might be able to take advantage of the 3DS’s 3D display; but I don’t think this is likely.
4) Yes
Backwards compatibility has been a big feature for Nintendo, and Nintendo has retained backwards compatibility when it was cost effective.
5) Its possible
I’m surprised that Nintendo hasn’t connected the DS and Wii yet because it seems like an obvious thing to do; but I wouldn’t be surprised if it hasn’t happened because Miyamoto, Nintendo’s internal developers and third party developers have shown little/no interest in this feature.