Voyager is likely to be done first in HD I think.
It would be cool to watch some of those battles in HD glory however.
DS9 shouldn't be any harder to remaster than TNG until the last couple of seasons when they made the switch to CGI. Voyager switched to CGI earlier in its run so it'd probably be harder to do due to the sheer number of episodes.
with CBS Digital suggests that DS9 will be next at around 16:20. "I think there's going to be more of this, Deep Space Nine there's talk about already."