I hope they will do the transition from CVS too.
Using OpenBSD for servers at times their use of CVS has never been an issue for me. So I get it, it's not the newest tool around, but if it works, is understood, maybe there's no immediate need to switch? The same crowd which says "they should just use git already", would probably follow up with "and how come perl is part of the base system and the pkg manager is written in it?... could we get Rust into the kernel while we're at it?"
OpenBSD's conservatism is what makes the system so immensely well documented, vetted, therefore secure and easy to use. They may switch at some point, and if they do it will be swift, and done right. But if I think about it: as a user I don't really care. It's not a huge deal to me what they're using for source control.
For a tightly knit team working with a central repository, CVS is just fine. Moving Python from CVS to SVN to Hg to Git gained nothing and made the development process so complicated that it was necessary to introduce even more complication by scripting it.
I get that github is probably the "lowest barrier to entry" here, but providing the "lowest barrier" is probably not even in OpenBSD's interest here. It's the same with some operating systems not providing graphical installers and whatnot. I could see not using github in a similar light here. If it's a simple bug fix or a one line change, reporting it is sufficient, a dev will fix it. If one's engagement is supposed to go much further, I don't think CVS is such a big hurdle? Or am I misjudging here?
Also, practically speaking, CVS is trivial to use, you can learn whatever you need in 5 minutes and never think about it.
BTW: Those rust, git enthusiast are those who never work on the project in the end, the are evangelists not makers.