"will the dividend date be set in stone as it is announced?"
IMO, yes. A date will be set. To get better idea, how it works...look at the company ZOOMD which has implemented spun off dividend recently and they set the date as Sep. 21 where as many people would have sold in between 9/13 - 9/17 when the stock price went high.
"if you don't own any shares when or if this is spun off, it will be too late to get shares and obtain dividend. Reward for LONGS. IMO."
Could be yes...IMO, companies like to reward longs and not flippers, shorts :)