The rumor du jour coming out of Tom's Hardware is that Apple is going to replace the current Mac Mini's Core2Duo with a dual core Atom 330-type processor. This is kinda like going to the garage and having having your BMW 328 engine replaced with that of a Toyota Corolla. The 1.6GHz Atom 330 Processor witch is in the ION platform is slower than even the current Mac Mini.
So, unless Apple is going to be turning the Mini line into a low priced Net-top set of devices, it wouldn't make sense to put a slower, cheaper processor under the hood. Even with dedicated NVIDIA 9400N graphics and all kinds of tricks, that thing would chug.
Check the benchmark