Hi, I want to sketch on paper, then scan it on a printer, then sketch and draw on inscape. Can someone tell me, what should I do when opening the scanned image on inkscape? I mean how to trace on it? Should I open a new layer?

Opening a new layer is not that necessary. If you move the image by an accident, you can correct the positioning by writing in the (0,0) position in the top row.
It is an option only to create a new layer and moving the image to that layer, then closing it. Layers are more complicated in inkscape than in gimp, I wouldn't use it for such simple task.
There is an auto-trace bitmap optinion in the path menu, but I wouldn't suggest that. The best result will always be doing the job manually.
The tool to draw paths is available with Shift+F6. You will need to draw every single outline as you would cut the drawing from different coloured papers and put them on top of eachother.
For the tracing, I suggest to use no outlines and a vivid colour, with an overall transparency. You can set it in the Shift+Ctrl+p panel at the pen tool, from a selected object.
Tracing is about using the pen tool to draw the path's nodes by clicking on each, and then adjusting the curves with the node tool.
For more information, see what the manual can say about editing nodes: http://tavmjong.free.fr/INKSCAPE/MANUAL/html/Paths-Editing.html#Paths-Editing-Node

Thank you. What are the features in the next version of Inkscape?

I'm not sure what all is expected. For one, we're expecting a new renderer, which we hope will help with a lot of the performance issues we have now. There are some other things as well. I'm sure you could find them on inkscape.org