without knowing what ports your tv or audio system have, there's no way to answer this.
look at the
tech specs page for apple tv and see what matches up to your equipment.
Apple tv is limited in the formats it can play. If you get all of your media from the itunes store, you'll be good. If you get it from other sources, you'll probably have to convert the files before you watch them.
look at reviews online, see if the arguments made make sense to you, make a decision on your own.
as far as waiting for the "new iTV box", apple
typically announces new ipods in september, and that would be a good time to announce a new apple tv product, but as of now nothing is announced, the new apple tv rumors have been going for quite a while now. so if you think you'll be happy with the current hardware then buy, otherwise wait till the
expected ipod event in september. and make a decision then.
the other option, is to get the correct cables, and an apple remote, and just hook your macbook up to the tv, front row is pretty similar to the apple tv interface.