AT&T and CYCL both said recently that the merger deal will happen early Q4, 2009:

“… AT&T and Centennial Communications Corp. (NASDAQ: CYCL) announced today that, assuming timely satisfaction or waiver of all remaining closing conditions including receipt of the required regulatory approvals, they now anticipate the pending acquisition of Centennial by AT&T to be completed early in the fourth quarter of calendar year 2009. On November 7, 2008, the two companies entered into an agreement under which AT&T would acquire Centennial. Under the terms of the merger agreement, Centennial stockholders would receive $8.50 per share in cash. …”  (full Business Wire article)

I plan on keeping my recently purchased shares until the $8.50 is hit or the deal consumates.