Currently, if an owner has a solid team, in my experience, the owner has to make some painful cuts to get to a 27 man roster after the rookie draft. It is often a good prospect, or a vet that had an off year, yet still has alot of career left. In the past, I have picked up solid prospects in the free agent draft after they were cut by their owners to reach 27 man limit. So the turnover does occur with the 27 man roster.

I would not like to see the roster limit reduced for the following key reason...
it would tend to reduce the likelihood of building a long-term good team, and tend to make every year or two tend to be the limit on keeping a solid team together. Sure that builds competitive balance for those with Attention Deficit Disorder, but I find a lot of the fun is keeping a team together for multiple seasons. If you have a long term team stategy, you assess your players, see guys reach the end of the line, and try to draft prospects that will gel in 1-2 seasons to replace your vets. If the roster limit is reduced from 27 after the rookie draft, a team will virtually have to continually dump their developing prospects...and hope to replace them in the free agent draft. Then, if they don't pan out next year, back they go...turned over again. NO LONG TERM TEAM DEVELOPMENT PLAN. That takes away alot of the fun of the sim in the first place. Why bother scouting...if you can't benefit from your baseball knowledge, and the sim becomes a strictly one season launch league (nearly).
Just my opinion.
Keep the cut limit at 27!!
Gary