This is a highly requested feature, and it's already been marked as planned on
a similar suggestion.
You can stay up-to-date on the development status of this feature through
CubeCraft's Public Update Board.
Currently, private games are marked as "Backlog" there. This has the following meaning:
"The Backlog contains ideas that we’re planning on working on. We can not assure that this will 100% happen, but as soon as it appears in the Backlog column, the chance gets bigger!"
We can conclude that there's a fair chance that we'll see this feature sometime in the future
I stole this reply from @Frontlane, I stole it because it's well explained :D