The ones with 32bit chipset are very old, the first gens of MB. Don't worry, the new MBP will run SL perfectly fine.
Can't we just restrict the usage of the word old to toilet seat iBooks and black powerbooks ?! Otherwise my white '06 Macbook will only grow more and more depressed. I fear this may lead to an acceleration in its development of new 'skin wrinkles' (aka cracks) and it's already doing that quite fast enough for my taste...