I don't think he meant that the quality etc. of things should never get better, that we shouldn't have gone from VHS to DVD. He just means that everything you have shouldn't be obsolete just because something new comes out.
Or, maybe DS9 doesn't look as good as ENT HD does, but that doesn't mean it has to be remastered to the point of being totally different either. If I record an episode of DS9 onto a DVD, I can watch it okay on my computer or TV screen. Its not as good as some other things, but it is watchable.
Star Wars- taking out old Vader guy, and swapping in Canadian dude, Hayden whatever is what I think he doesn't want to happen. And if that's what's going to happen to DS9, well then maybe we should leave DS9 more or less alone, as long as it's not unwatchable in HQs.