Nobody really knows if this wide touch-screen iPod even exists.
The only thing even vaguely resembling confirmation of anything was a remark out of Foxconn about a "none touch" iPod, and "none touch" seems nonsensical, or perhaps the result of a botched translation.
[ Edit: "a none touch concept" could refer to automated assembly methods, or even the little carrier that suspends the new nano in its display box. Terry Gou didn't even mention interface in that blurb. ]
Is your 4G full?
Do you really want to watch video?
When you listen to music, what % of the time is your iPod screen where you can see it?
I'm in a similar position. My 4G still has space for music, I'm not that bothered about video - if I need to take it with me, I can stick it on my cellphone, and most of the time, my iPod is in my pocket so I wouldn't even get the benefit of the coloured screen.
I'd say that you really need to think about if you will use it for video. Remember that you can listen to music while doing things, but video takes all your attention. That really only is possible and useful if you have to wait around for a long time, or spend time on (safe) public transport. Otherwise, the 8Gb Nano seems like the most attractive model at the moment.