Retain the cash for what purpose? The cash is worth only what it's worth, and has been accumulated for the purpose of an acquisition. And more cash will come over time - a lot more IMO.
The shares should be worth progressively more over time, well over possible interest earned from cash in the bank.
As for 31 May, as I have suggested, the issue is IMO moot. Swartz has zero say per the agreement (if still in force) IF it's an all/mostly cash deal and all BoD members agree to the action.
Also consider this: with the obvious volitility of our PPS over time, would a prospective candidate for buyout want shares, or cash? To them, the shares would probably represent risk. Cash=no risk.
JMHOs,
SGE