Ann: S&P DJ Indices Announces December Quarterly Rebalance, page-8

yes that's right, it will now be on the list of instruments, however that does not mean it will automatically be bought.

There will be heavy volume at the time of inclusion, this is mostly by market makers covering a new wave of instruments that will be issued, and a mix of some funds that are required to hold for weighting purposes. This all happens pretty much in one day, sometimes two. Many of those trades will be organised before hand and will simply be crossed through the market.
After that's over, inclusion is pretty much forgotten.