GitHub has gained near-monopoly status because it has provided a superior user experience at a great price. If either of those value propositions start to crumble,
git remote add ...
(One issue is that such a DSL could only provide lowest common denominator functionality... or else, suppose CI providers 1 and 2 offer feature X but 3 and 4 don't, then if you use feature X, you can switch between 1 and 2, but the tool would give an "unsupported feature" error if you tried to generate output for 3 or 4.)
My argument is that technological platforms are pretty special when it comes to monopoly power because their lock in/switching costs are so high that they can last long after they've stagnated in terms of innovation.
And they just buy up all their competition.
Surprised no one has taken facebook's launch strategy. Only allow it in one school. Then only ivy league colleges. Then all colleges. Then everyone. Also allow you to import in your email contacts on signup.
That strategy created press / word of mouth and kept it youthful until they were ready for the big launch.
Epic appears to be firmly pro-developer, which no matter what Tim Sweeney says isn't currently translating into an improved consumer experience.
Being too pro-consumer on the other hand... well, that gives you mobile gaming with heavy focus on free-to-play and plenty of ads.
Be careful what you wish for :)