Most of the successful open source projects either come from large scale IT companies or academia, so they gonna continue open sourcing and collaborating to maintain the community anyway.

So, as far as there are companies running on-prem technology (or use raw VMs w/ services in the cloud) and find it meaningful, open sourcing & the community will continue to exist among the bigger names. Small companies are not key players in most big data open source anyway.

Also, this seems to be a discussion between - commercial software vs open source software, similar to Windows vs Linux. You pay for what you get. If you adopt a commercial software/service, it is guaranteed to provide better service and UX; if you take the OSS route, you have to eat the bullet of taking care of the system of yourself.

In the end, it seems to be all about $$. If cloud providers evolve to a stage that it doesn't make sense for non-cloud provider to develop their own technology, the open source projects around data would fade. But the gap is huge, on-prem storage is still at most 1/4 of the cost in cloud.