Usually when a revision to an architecture is put into place, there is a significant amount of time before the majority of machines see the benefits. This is due to a few reasons, such as vendors needing to exhaust supplies of older units. Because of that, shipments are slower due to less demand for the newer CPUs. Santa Rosa is expected to make much quicker progress than usual, however, particularly in the mobile front.
Next year, it is expect that Intel's 45nm process mobile CPUs (Penryn) will account for at least half of total shipments. That's a brave statement coming from a chip that is as of yet unreleased. Intel isn't making the claim, however - It's coming from notebook manufacturers. Since they dictate what they buy, it might actually happen - and the benefits of the Santa Rosa platform might bleed their way into the market very quickly.
Considering the advantages the new CPUs offer, particularly on the mobile platform, this wouldn't be a bad thing at all.