Newsletters can be pretty effective. We have a monthly newsletter for our game (
http://www.spacesofplay.com/newsletter) that both fans and some journalists subscribe to. Open rates are between 40-60%, click rates between 10-25%. (The most popular links in our newsletters are when we talk about other games that we like.) At the very least you should let people signup for an email reminder for when the game releases.
Do you use any third party tech to organize and send out mass newsletters? I've had MailChimp bookmarked for a while but I haven't really reached the subscriber scale where I need that sort of power. But, at the same time, getting surprised with a large burst of subscribers would be an unpleasant surprise to someone like me doing everything near-manually through Gmail Groups.