That is an all around terrible idea for those players if they are truly willing to sit out.
1. They are going to be a few months older by that time. This is especially a problem for pitchers who wouldn't be keeping their arm loose and up to normal standards by pitching in games.
2. Why would they think teams will pony up $20, $30, even $40 extra million at that point if they won't now?
3. I have to imagine teams won't budge at that point because there would almost certainly be some disgust/annoyance from teams that players are turning down what the market says are already fair offers.
Hearing that JD Martinez thinks he's worth $30 million/season is just mind boggling. The dude will be a DH for an American League team. He's not worth that. Boras is filling these guys' heads with delusions of grandeur.