The idea is to provide a platform where new ideas can be tried out without the stringent backwards compatibility constraints of the regular Scala releases. At the same time this is no "castle-in-the-sky" project. We will look only at technologies that have a very good chance of being beneficial to Scala and its ecosystem.
My goal is that the focus of our research and development efforts lies squarely on simplification. In my opinion, Scala has been very successful in its original goal of unifying OOP and FP. But to get there is has acquired some features that in retrospect turned out to be inessential for the main goal, even if they are useful in some applications. XML literals come to mind, as do existential types. In Dotty we try to identify a much smaller set of core features and will then represent other features by encodings into that core.
Right now, there's a (very early) compiler frontend for a subset of Scala. We'll work on fleshing this out and testing it against more sources (the only large source it was tested on so far is the dotty compiler itself). We'll also work on adding transformation and backend phases to make this into a full compiler.