In a press release that came out a few days ago, the Zwift announced that they would be adding new circuits for these races. However, Zwift has not specified whether new roads will be released or just new routes on existing roads. This article contains some speculation about what new roads Zwift may release.
I think that it is quite unlikely that Zwift will release new roads when they just released the Urukazi expansion to the Makuri Islands. If Zwift does release new roads, I think it will be a completely new world, similar to Crit City that is solely built for races.
None of the three routes that are supposed to be used have been announced yet, leading me to think that Zwift is going to release this in the December game release. The December game release should be releasing around the 7th or 14th.
Race 1: Rolling Circuit // 13.8 km rolling
Race 2: Hill Climb // 8.5 km, 162 m
Race 3: N/A