If you look at the SEC filing,
Each of the Company, Rightmark and Merger Sub has made customary representations and warranties to each other in the Merger Agreement. Completion of the Merger is subject to customary closing conditions, including, but not limited to, (i) adoption of the Merger Agreement by the Company’ stockholders, (ii) the absence of any order or injunction prohibiting the consummation of the Merger and (iii) truth and correctness of each party’s representations and warranties at closing. The Merger Agreement may be terminated under certain circumstances, including, among others, termination by mutual agreement of the parties, termination by either party if the Merger is not consummated on or before April 20, 2012 and termination by the Company at any time for any reason on or prior to May 4, 2011, as set forth in the Merger Agreement.
It is safe ONLY after May 4 (IMO) and that too if no lawyer/court orders are involved prohibiting it etc., otherwise it is risky. Maybe that is the reason CSR is not trading at expected merger price..
"Correction": Also if the merger is not consummated by Apr 20, 2012 - this depends on shareholder vote and other details, merger can be terminated. But chances of that seem slim.
Also, the earnings of the company, due on Apr 25th might be another factor in the stock price.
Disclosure: I have no positions in CSR and no plan to initiate any positions.