What's the leverage? Taking the license away? Why would they do that? Doesn't make any sense. Even if Sony said no to multiplatform, it's hard to see MLB cancelling The Show. I very much doubt there was any kind of "forcing" at all.
They could have easily given the license to make MLB games to EA, 2K or someone like that.
Sony and MLB just made a deal to extend Sony's rights to have the license for the game, at the same time Sony announce the game is coming to other consoles. "Forced" might not be the right word. But it's obvious that MLB would be the party interested in getting the game out onto more platforms and during negotiations they got that wish.
Sure, they could sign a deal for another publisher to make MLB licensed games. But why would they cancel The Show, which has been around since the 1990s?
They don't like money? They don't want a high-quality franchise with a loyal following associated with their product? I suppose it's possible that a big-time publisher with a lot of capital made them an offer while demanding total exclusivity but has the recent history of MLB video-games really been so lucrative to the point that such an scenario seems likely? Has it been so lucrative that Sony would feel pressured to bend over backwards to do something they really didn't want to do?
I just don't see the leverage.