Because after Kevin publically trashed the company's business prospects during the past 2 mos, if it is not approved the stock price will drop to about 5. The institutions wouldn't like that, so they'll vote yes.
A certain date for closing has not been set. Then there is the uncertainty of lawsuits. One of the opponents could (I'm not saying "will", just "could") get an injunction against closing, pending filing their lawsuit. So depending on whether the opponents continue to battle, it might be a while. Assuming nothing like this happens, here is what the announcement said:
"Following the closing of the transaction, Clayton's stockholders of record will receive a Letter of Transmittal by mail with instructions on how and where to forward their stock certificates to receive the $12.50 per share to which they are entitled."
I presume that as long as trading is still available, you can sell your shares in the market and get your money a lot sooner than if you wait for some letter. The only reason for holding as long as trading is available is if you think the opponents will eventually succeed in overturning the vote, and that some white knight will come to the rescue. Not real likely, IMO, but a lot of shares are still being held, so who knows?
As to what to do with your cash - heck, I'll take it!