Ok so here my 2c...
I fully support the move to GitLab, but not for any real reason to do with Microsoft acquiring GitHub (although i do get others concerns). For me it's more about the project management aspect of UBports.
GitLab supports groups and subgroups so it's easier to organise our 300+ repositories, making it easier for everyone to find their way round, and also visualise the different parts of the project/platform and how they fit together. There could be groups for Unity8, System Apps, Core Apps, Packaging, Infra, Documentation, Tooling, Working Groups, Experimental... the possibilities are endless but each group is easy to digest and only contains repos specific to each groups goals. On GitHub you just get a giant list of all repos and you almost have to remember repo names as paginating through the list is just painful if you can't.
GitLab supports issues, milestones and kanban boards at both group and project level. This makes it really easy to organise per project as well as at the group level and get a higher level view of what's going on. You can also move issue between projects which is handy!.
GitLab CI would also be a great thing to have at the project level. Each project could define it's own pipeline for merge requests, doc generation, building and publishing clicks to open-store etc... and not have to use an external tool like TravisCI. Jenkins is probably still the right tool for the building ubports repo and could continue to build debs on changes to master, xenial, bionic branches. But allowing a project to define it's own pipeline, even attach their own hardware via a dedicated gitlab runner in my opinion is quite a powerful thing. Members of the community could even offer up spare hardware and create a pool of runners for UBports
GitLab releases new features nearly every month, so things can only get better.
GitHub is serving it's purpose right and doing the job ok, so it definitely doesn't need to be rushed if a decision is made to move.