It'd be great to see a mini dreamcast be released, I think it would sell really well. 
SEGA were notorious for releasing too early, and having all of their competitors release slightly better systems for cheaper a year later. MegaDrive (vs SNES), Saturn (vs PSX) and DreamCast (vs XBox/PS2). All great systems that were eclipsed by competitors consoles a short time after.
A re-release of a cheaper mini-Dreamcast would be great. I think the DC can still hold it's own against the PS2 and XBox. Even moreso if the new 400MHz SH-4 chips that are being used in the automotive industry are used in place of the original 200MHz versions, retain backward compatibility while allowing for even more complex games and graphics.
If this is all true, and they appear for the right price, I'll buy one for sure, even if I already have an original DC.