We WILL have a Joomla 3.x ready version of DT Register. When? Can't say quite yet. We ARE working on it presently and going through making the necessary changes. There are a bit more than we had hoped for. As we get closer to it being ready, we'll post updates on our site about upcoming availability.
We certainly wouldn't recommend any live site to run on 3.0 at this time anyway, so it shouldn't be a major hurry for anyone at this stage, but we'll have a version ready ASAP.