By moving now you're doing a number of things. First, you're telling your contributors and users that you don't like having access to your software controlled by MS. Second, you're supporting their competitor now when they need you, rather than when you need them. Github's competitors may not be around in 5-10 years when you will finally need them, unless they are supported now. Thirdly, it tells MS that you will move if they meddle again, if everyone jumps ship for gitlab et al. then they are much less likely to buy gitlab down the road.