The whole change in the self-hosted license new terms is to ensure that it remains viable in the future for us to continue to develop it. We want to support self-hosted as long as it is a viable option for us. As Marc already mentioned, we can't see into the future so don't know what it may bring and that is about as a concrete statement as we can provide you.
It could be that self-hosted sustains product vitality for many major versions to come. It could also be that many people flock to Cloud and 5 is the last one, we just simply can't tell you right now or provide you a guarantee.
We have stated that version 5 will remain available for the Classic license. That is some time around (give or take) 10 years of that software version. Many, many communities will rise and fall during that period of simply natural selection beyond the software's doing. I think it is a naive notion to state that you wouldn't start a community on our software, if you think it is right for your community, simply because we can't guarantee ~10 years from now it may not be available on self-hosted.
As a hypothetical, if we do decide to drop self-hosting, there is nothing stopping you from continuing to run version 5, switch to cloud, or switch to another community software provider. Again, this is a completely hypothetical because there is nothing right now saying we will or will not continue providing self-hosted.
Ultimately, my point is that if you see our software as the #1 option for creating a community, the ~10 years of version 5 is so far in the future, why not give your community the best chance to start? Maybe in 10 years your community is successful enough that Cloud is a completely viable option. Maybe your standpoint on running a server changes and Cloud is a much-appreciated option. Much can change in 10 years, keep an open mind 🙂 .