Alain Jarniou, Director of Test Drive Unlimited 2, has stated in an interview with VG247 that there will, in fact, be an open beta for Test Drive Unlimited 2 coming sometime this year. The open racer will take place on a massively scaled land, and feature MMO style free roaming servers to drive and walk around in to interact with other players.
There hasn't been any details released yet on when or what system the game's beta will be taking place on, but Jarniou says that it is only due technical aspects that they haven't quite pinned which system the beta will hit. So, currently the beta's anticipated announcement of which system and time it will hit is "soon".
Test Drive Unlimited 2 is scheduled for a Fall release on PlayStation 3, Xbox 360, and PC, so there is a lot of selection to be determined for the beta. Hopefully with a Fall release, this open beta will hit soon to work out a lot of the online kinks before the game reaches a final release.