First of all if you're in the world series, I highly doubt that you are going to being leaning heavily on late season callups, unless you ******* suck and got to the world series through sheer luck, in which case just be glad that you luckboxed a WS trip and STFU.
As somebody who routinely goes to the world series, anybody that is important to my postseason roster is somebody that I normally will want to keep in the majors next year. The one time I had a tough decision was when I had this guy sitting in the minors
whatifsports.com/HBD/Pages/Popups/PlayerProfile.aspx
He was ML ready by the time the postseason came around, but only had 1 option year left. So if I called him up, I would have an extra quality arm in my pen. The risk was that if I went to the WS, I wouldn't be able to demote him for the first 20 days of the following seasons to delay his arb clock. As it turns out, I won the WS and by the next season he was out of options and his arb clock started a year earlier than I would have liked.
Of course it would have been easier on me to just win the series and then stash him immediately in AAA, but that was the type of decision that I enjoyed making. I already manipulate the system in HBD so much that I don't think it hurts to have a few less opportunities to do so, esp when it's offset by the fact that my ML team made the world series.
Other than that last year I demoted this guy before game 6 and played with 24 guys because he was a worthless piece of **** that I didn't need:
http://whatifsports.com/HBD/Pages/Popups/PlayerProfile.aspx?pid=2840735
If you don't want to pay a guy $327K next year, don't bring him on your playoff roster, problem solved.