Not sure if this is going to rock anyone's socks, but the Dreamcast got a new shmup by NG Dev-Team, the guys behind Last Hope. You can buy it on their website or on Play-asia. They were crazy enough to make a Neo Geo version, too, for the low, low price of 320€! The Dreamcast version is obviously far more cheaper.
If you're going to buy it don't forget to post some impressions here so the community learns more about the game. It's not like any review website will bother with it.