I do think I see an avenue to a salary cap in baseball similar to the one we see in the NBA.
In the last few seasons, we've seen a lot of mid-level (sometimes higher) FA have to play the waiting games and settle for far less money for far fewer years than they were hoping for. The MLBPA has been vocally displeased with these occurrences.
A solution to that is a salary cap (hard or soft) and a max contract.
Without a max contract, teams are rightfully giving all their money to the top players while a large percentage of players are left to fight for scraps. I have to imagine the player's association will look at ways to remedy this in the next CBA.
I don't even think you'd need to set that low. Obviously it'd be tied to revenue, but I'd be fine with the cap being $250 million. The real key is the existence of a max contract.
Now, I'm not even sure if a max contract is a positive for competitive balance. We've seen its impact on the NBA, and I wish they'd get rid of it. I'm just saying I don't think some sort of cap or max contract structure is that far-fetched given the recent complaints of the player's union.