With Q1.2014 you will able to implement custom Azure, Amazon or Everlive storage provider and will have access to the uploading file/chunks. Regarding to the progress bar for now it will not be possible to implement it in the described way. We could track only the progress where the file goes to the uploading handler. For the next versions of the control we plan to implement direct upload from the client side. This process could be tracked more precisely.
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the UI for ASP.NET AJAX, subscribe to the blog feed