Would they let us know if there was a DNA match? In most cases, I'd be inclined to say no. But the information released by this LE agency exceeds the norm. In fact, as far as I know, Chitwood is the only LE authority in the area even to use the word "serial killer". So I have a hunch that if there were a DNA match, the public would know. It's hard to guess, though, because so many factors could come into play. At least he did acknowledge the possibility of a connection to the earlier murders, which says he's keeping an open mind and will take measures to confirm or rule out a link.
That's a good point about Chitwood. From the videos and interviews I saw I liked what I heard out of him, he seemed to have a good grasp on the situation. My line of thought was, If they knew it was connected they might have wanted to keep pressure off the dept. from the media and everything else that would come from the announcement for a time so they could work the case on the down low. Noting the lack of success in the previous tactic of media blitz. I think you're right though, they'd probably let it be known if they knew it was connected.
With her situation such as it was it might be difficult to get a conviction if they did find a match to some random DNA, a match to our guy would of course sweeten those chances if they could ever find him.