No it doesn't mean that.
Visual builder could be deprecated the same way as any other (experimental or non-experimental) feature. In fact experimental features might be a bit more likely to be deprecated.
But we also check around the usage of the visualization, and we know that Visual Builder is currently used rather often, so it's unlikely, that IF we would deprecate it, that we will remove it without at least having a majority of the same features in other parts of Kibana. And most likely there will be a rather long time between deprecation and removal of the feature (aka a major version at least).
To be a bit more specific about Visual Builder: We are currently looking into building a new editor (https://github.com/elastic/kibana/issues/17076) which will be one of the long running efforts during the 6.x lifecycle. Once this is done, we are trying to align all charts on the same editor again (instead of having that unaligned and fragmented UX in Kibana, meaning we will try to merge the features we have in Visual Builder into the core visualizations (or vice versa, but with one editor for all). And if we would then figure out, that we have the majority of features available in all visualizations, we would reevaluate what use-case Visual Builder still provides, and maybe that wouldn't be enough to keep it alive.
But as mentioned, this is a super long running effort, so I would say, you can safely rely on it being still present in the upcoming releases and you can be rather sure, you won't see any deprecation warning before there is a near feature-parity with the new editor (or other parts of Kibana).
Cheers,
Tim