An Old Rumor is Back: Ultra-Portable Notebook from Apple

MacScoop as well as MacOSXRumors claim Apple would release an ultra-portable notebook in a near future. This computer would feature a 12" display, should be of course thin and much lighter than other Apple notebooks.
Despite its size, it should keep its built-in optical drive as well as dual core CPU, making it a miniaturized MB Pro, at bit like the PB12" for the PB15".
The price should not be that small, and is estimated around 1800$.
This ultra-portable will hardly be thinner than the MB PRo, one can only reduce it by 2-3 mm, some parts can not have their height reduced on-demand, such as the optical drive (minimal size: 9.5mm). The screen panel can be reduced if Apple removes the integrated iSight, but it can not really be justified.
Regarding hardware parts, thanks to Transcend and its recently introduced 1GB Micro-DIMM memory modules, one can save up to 40% space compared to DDR SO-DIMM modules. To avoid large cooling device over the CPU, one will need to use Ultra Low Voltage CPU version from Intel. However, the only ULV CPUs currently available are based on Core Duo (Intel® Core™ Duo processor U2500, 1.2GHz, 9W). Without mentioning that Apple will have to integrate high-tech batteries, providing the best compromise between size and lifetime.