According to a listing in Target's inventory system, a 250GB PS3 bundled with MLB 10 The Show is coming out on June 13 for the price of $349.99. Though just rumoured, the shipping lists seem to show a pretty solid bit of evidence on this upcoming bundle.
It also makes sense for a bundle featuring an MLB game, since the PlayStation 3 now features the ability to watch MLB games right on the system with an MLB.TV account. This will also help sweeten the deal of the 250GB unit by including a "free" game.
One big note of speculation however is the price. Will it stay at the $349 price point, or is this scheduled to be a lowered price bundle to be offered by Sony, since their press conference for E3 takes place only two days after this scheduled release. Currently, Sony has not released any speculation regarding this rumour, but then again, isn't that always the case?