If you are using Azure DevOps keep using it, no point mixing Azure DevOps with Gitlab.
Azure DevOps isn't going anywhere anytime soon, In fact, its actually getting better and is getting new features. Not at the same rate it had before GitHub purchase, but even in recent Ignite event, MS has said it is brining GitHub Security tools into Azure DevOps, so I wouldn't go a head and quickly go with statements like "I don't think it has much of a future".
MS has a HUGE client base in Azure DevOps and some of the abilities will always stay there and you will not see them in GitHub and other way around.
I would say MS is bad at official announcements so most of what you hear and see are assumptions or internal misalignments between MS Sales and GitHub Sales. But I know they are working and its just matter of going to the Azure DevOps public roadmap to see.
I suspect we are going to see Azure DevOps v.2 at some point to make it more stable, reliable and secure like most cloud based solutions that have been up for quite a few years, you are going to eventually get to "feature complete" state where there isn't a LOT of innovation left to do, just small increments of updates.