Creating next generation issue trackers, search, build solutions, etc. requires significant R&D and I really don't think GitLab is focused on this type of skunk work. I personally think Microsoft has the best chance to disrupt the software development lifecycle in the future, due to their R&D budget and talent pool.
GitLab in a lot of ways, is sitting in a perfect business position. All they have to do is look at what Atlassian, Microsoft, GitHub, etc. are doing and copy what can be copied. There really is no shame in this, as this only makes business sense.
Git has created an opening into the software development market that has never existed before. In the past, you had to spend a lot of time and money to create a version control system, which you could use as a beachhead for Enterprise sales. However with Git, you no longer require significant time and money to compete.
With Git, the really hard stuff is being worked on for free, by some of the smartest people around the world. And because of that, you can focus on solving the not so difficult problems, but still problems people would pay for.
Git has created a massive opening for who can compete in Enterprise, but as the easier problems get solved and turn into commodity features; focus should shift again, to the not so easy problems. If GitLab invests properly, they should be able to compete in the long run with Microsoft and others. The challenge I guess, is knowing when to start focusing on the harder problems.