It makes sense that they wouldn't have the channels available until 4/1 because that's a few days before opening day for the regular season.
It seems like they would make an announcement as soon as possible though. My MLB.tv annual subscription auto-renewed on February 28th. Many of the hardcore baseball fans who would be interested in EI will already be locked in with MLB.tv for the year before they even know Dish is offering this. There are probably people who switched to a different provider for EI already too.
Either way I would still choose MLB.tv over extra innings because I do have a good internet package and streaming devices. I like having both feeds for every game including OTA feeds, Canadian feeds, and RSN feeds that aren't offered on Dish. I also like the portability of the MLB at Bat app.
That being said, I'm glad to see Dish finally getting back on board with this. It's a good option for baseball fans who can't, or don't want to, stream their games over the internet.