This is foolishness. Holliday is a great left fielder no doubt, and would be a tremendous asset to the team, but you guys are seriously selling out to the greener grass on the other side of the hill.
Jason Bay is a consistent 30+ HR hitter year in, year out. He and Holliday have the same career high in HR's, but Bay has the second, fourth, and fifth most HR's in a season between them and has crossed the 30 HR threshhold two more times than Holliday has in a career track that has been as close to comparable as you're likely to get with two ballplayers.
Holliday is a good OPS hitter, but does not have that kind of raw power on his resume. Other than the truly awesome year in 2007, he's a slightly better offensive version of Kevin Youkilis, and I'm not sure what kind of "true #4 hitter" that makes him. (actually over the last 2 years I'd give the edge to Youkilis)
Also, this year Jason Bay had a slightly higher OPS than Holliday, in a tougher division. You lose practically nothing if you "settle" for Bay over Holliday.
I understand the sexiness of Holliday's batting average and his slightly higher OBP does make a difference, but what we're looking for is specifically a home run hitter. Both Bay and Holliday would serve more than adequately next year if called upon to do so and there are great arguments to go for either guy. Bay does NOT take a back seat to Holliday. He just has a different skillset.
Finally I'd like to point out that while Bay hit .267 this year he's a career .280 hitter. He's not THAT vulnerable. Even with that, he hit for more raw power than Holliday and got on base about as much.
I can't imagine that the team has done anything like stiffed or disrespected Bay when there's every possibility that he becomes the best remaining option on the market at some point in the offseason. If they did, it would be an incredibly stupid thing to do.