Great question, thanks for asking. I can give you my personal answer on this one, but I think we should write a statement about it as a disroot team also.
For me, (and I think others in the team too) we started disroot out of a personal need for such platform. (we've run similar "test" project in the past which we re-branded into disroot to become truly independent). We never were in favor of corporate emails and other such services. We've been always using volunteer based infrastructure. At some point we decided that we would like to create our own platform. Mainly not to depend on others but also because of the fact all those alternatives are usually closed for public account registration. We wanted to share our platform with people who don't have geeky friends who host mail servers, owncloud instances etc.
So as far as I'm concern disroot isn't going anywhere. It is my primary email address, xmpp account and d* account.
Would we just kill it? I don't think so
I think we have something, big corporations don't. We believe in what we do, and the change of current status-quo. Going back to the roots, to how the internet used to be. For giants like google only profit matters. If their service won't bring enough money they will simply shut it down without looking back. Just look at all the services shutdown by google until now.
We are not focused on getting as many users as we can, otherwise we shutdown the project. This is not our goal.
In fact we want to focus on convincing other collectives/groups out there to follow our initiative and create other, similar *public nodes** to re-create decentralized and federated nature of the internet.
Our growth is based on how much money we can get from all kind of sources (mainly donations from users and groups, personal investments). If we can't afford more servers to serve more people we will simply shutdown new account registration until we have enough resources to expand the server infrastructure.
Besides, small platform with small amount of users is easier to maintain
Of course I can't tell you 100% we will stay no matter what. But that's the case and risk with any opensource/volunteer project. We started disroot with "long run" in mind. From my side I can tell you, disroot is my baby and I believe in it's success (or however you want to call it).
You don't kill your babies.