The Droid name is licenced by Verizon Wireless. The Droid 2 could actually end up being an HTC phone if Verizon wanted it to be. There are talks of a Nexus with a keyboard being the droid 2(this would complete me), or a phone motorola already has made. The one Motorola is testing now is operating on 2.1, has similar specs to the Nexus, is touch only, and is due to be released world wide. The one that hits the states will likely be labelled the as a "Droid".
Greg, if you are worried about buying a phone just to have a newer one released dont worry. The droid is selling too well to jump ship. The nexus will probably come out next (would take the top spot on the touch only android phones), then a few others are set to be released later on. If I were a betting man I would say March for the Nexus, and late summer for the next Droid.