No one has any *definitive* insights as to when any aspect of Star Alliance participation will begin -- at most, we know at present that CO anticipates cooperation with Star Alliance member carriers as soon as possible after exiting SkyTeam. We simply do not know enough about the switchover to Star to be able to reasonably posit what might happen -- for instance, CO might enable full Star membership from Day One, or could ramp up commercial ties with the A++ carriers immediately then progressively phase in ties with the SQs/LOs/TGs of Star through the start of the 2010 Elite year, or CO could find the IT requirements for Star to foul up any attempt at a swift timeframe.

That being said, even if you were traveling in, say, May 2010, I'd advise against booking SQ in the hopes of getting CO mileage credit because SQ has, far and away, the most restrictive mileage earning structure of all Star Alliance programs.