i think this is a tough decision, and I've been wrestling with it too since it probably will be a year before the next release unfortunately. I personally will prob keep using my ipod classic until a new edition comes out.
I didnt think the ipod touch 4 was worth it for me when it first came it so i am trying to remind myself that if it wasnt worth it then, then it shouldnt be worth it now.
but it depends what you plan to use it for i guess, id like it to be able to replace my point and shoot. Plus 256 mb of ram is already behind the other IOS devices.
If you already have an earlier generation ipod touch then i dont think its worth it, ...or if there is any chance you might get an iphone in the next year or so.
good luck
***EDIT***
Going used would probably be the way to go on this if you really dont want to wait. I say be patient and find a decent used one.