They need to be careful putting too much Trek out at one time. We're already getting three seasons of TNG in 2013, adding Enterprise to the list isn't a good idea. As big a fan as I am, I'm only going to spend so many dollars on Trek regardless of how much is released.
I think CBS want to strike while the iron is hot, considering TNG remastered is selling so well and STXII is coming out next summer. ENT is something they could whip up very quickly in HD unlike DS9 or VOY.