From the official announcement:
The world’s expectations of software experience are being raised by advances in mobile computing. We are bringing that revolution to the Linux desktop: for window management and applications. Though our work at the application level has only just started, we are certain that multi-touch and gestures will be central to the way we use Linux applications in future.
Work has begun on all three fronts in Ubuntu, and we expect it to remain an area of active interest over the next few releases up to 12.04 LTS. Touch will be part of the Ubuntu Netbook, Desktop and Light products from 10.10 and beyond.