Azure DevOps and Github largely cover different, though overlapping market segments.
I would be slightly more concerned about Github Enterprise and Devops co-mingling over time, as I think that may be inevitable, which makes me concerned over the public/free resources that Github offers in the long run... even then, migrating to Gitlab is an option should that time come. My only hope would be better discoverability and social coding with Gitlab to better match Github over the interim time.
Even then, it's just a possibility and somewhat unlikely that MS would burn this much karma.