As long as BSD stays with BSD license, it won't happen.
Users really only care about cost of ownership, ease of use, support, etc. which is to say, they want to use what everyone else is using.
Many embedded systems and such use BSD because they don't have to release their changes as open source, which pretty much forbids their use of Linux.
If you meant by "servers" such on clouds, maybe it's already Linux only.
Users really only care about cost of ownership, ease of use, support, etc. which is to say, they want to use what everyone else is using.