According to the XNA team at Microsoft, we will see an update of XNA Game Studio Express somewhere in April of this year. Looks like the members of the XNA team have seriously taken into consideration the feedback coming from XNA Game Studio Express users. I assume that there are quite many improvements. From the most important improvements (at least from my perspective), I would mention the following:

1. Full support for Windows Vista. (Cool, I can now upgrade to Vista as I was reluctant to do so because of XNA Game Studio Express).

2. Bitmap font support (at the moment, as you might be aware XNA does not support bitmap fonts, so we have to resort to our own implementation or third party solutions like Nuclex fonts).

3. Math API improvements. No specifics on what is improved but...

4. BasicEffect will support per-pixel lighting, which is fantastic.

5. Support for volume textures (Texture3D).

6. Ability to read Vertex and Index buffers from Model types.

7. Sharing games with other developers will be extremely easy. It will be possible to package games in a single file (which can be downloaded or sent via e-mail).

Well, this list is not complete. You may wish to check out the post at the XNA Team Blog for a more detailed list, though I believe even that list does not fully describe all the updates that we will see shortly.