I didn't go for a DSLR yet both because of the fact that I'm lacking of time to use it, and also because of the lack of a really great camera in the market.
Live preview is getting more popular in the market, and I believe it's really useful for astrophotography, it really saves a lot of effort, making a DSLR even more standalone. Right now people depends on a notebook PC with suitable software to really focus a DSLR, however, with Live preview, things should become much easier.
Frankly, what makes a DSLR a SLR is the traditional through the lens view finder, however, it's not necessary and I would better say, it's useless for astrophotography especially with Live preview. So, all we need is a big sensor like APS-C or bigger, and an inter-changeable lens system so that we can connect to our telescope's prime focus.
Having said that, such a camera will become more like a regular DC with a bigger CCD/CMOS and an inter-changeable lens. It will probably allow you to record video clip as well. ;-)
Such an animal should be more compact than existing DSLR, but yet at least as powerful as a DSLR, and far more suitable for astrophotography.
To be more realistic, so far Canon 40D is the best one available from the market.