The characters from Beast Wars are from the time period after the Great War had concluded. Through some transwarp bullshit or w/e they went back in time to before the characters in the Ark from Generation 1 woke up. I.e., prehistoric earth. So Beast Wars has future characters, but its almost like a prequel. DN
The Great War between Autobots and Decepticons ended 300 years earlier, and their descendants - the Maximals and Predacons - have an uneasy peace, the Pax Cybertronia. The Maximals and Predacons are roughly two generations on from the Transformers shown in Season 3, if you go by Rattrap's "Great Aunt Arcee" quote. A few of the G1 guys are still alive and show up - the main one is Ravage, also Grimlock in the comics, and according to their profiles, the Magnaboss group. The plot also ties into G1 throughout the end of season 2 and the whole season 3. It's time travel, and also there is some very cool stuff involving a certain Decepticon warship... Also, Starscream's Ghost makes a cameo in Season 1. Can't forget that!