Santa Rosa MacBooks would be coming in November at the earliest. The only upgrade that Santa Rosa would bring, though, would be X3100, which is still subpar to a discrete chip, but still a slight upgrade to the GMA950 of the Napa MacBooks. Processor speeds would have a slight but insignificant increase. Although LED monitors are likely to be added on, too, which would give probably a 30-minute boost to battery life, if the MBP is any indication.
I just opted to buy my MacBook now and get Leopard later.