They should get the funds placed in escrow.
Of course, I am confident that no matter what happens, the acquiring company will have the cash lying around to pay off my bonus. A small consulting firm... not so much. Regardless of the contract terms, the firm can always declare bankruptcy, in which case the employees expecting their $50K payout can stand in line with all the other creditors.
Yeah, escrow sounds like a good idea for a case like this. (Would escrow be enough to shield the money in case of bankruptcy? My Google-fu is not helping.)
Paying a dividend knowing that it would result in the company being unable to pay its liabilities is therefore a breach of that fiduciary duty.
However, even if there is a contract I bet it allows staff to be made redundant if the company decides not to do something without getting paid out, so that would be a possible loophole.