Several times I've heard (and have personal experience with) how hard getting older Windows games to work is on modern PCs. All the work that people have put into ScummVM and DosBox is amazing, and there isn't anything like that for early WIndows games. So GOG may be hitting a point where they've got most of the big-name early games, and are now hitting their heads on technological issues with 16-bit WIndows games.
They can't stop releasing games, so they're including more indie games and the early 2000s games. Both of those categories are more easily compatible with modern systems, although they come with new headaches of patches, more complex mod support, no ability to control config files, etc.
I definitely think the plan going forward is to incorporate as many kinds of games under the DRM-free umbrella as possible. They're not going to give up on old games certainly, but they are going to be having a wider variety of releases.
I have really appreciated how the GOG team is still curating the games catalog. GOG is focusing on the 'Good' as well as the 'Old', and that's fine with me.
I would still really like to see Cyberstorm here though.