What will Wikipedia be like in 2030? What could it be like?
I'd like it to be one wiki.
Instead of many silos, separated by language and project, we would feel like one community working together. Although under the covers we may still have separate databases and archives, from the user perspective there would be no barrier between projects or languages.
Machine translation and network bandwidth will have continued their progress, so any content will be available to any user anywhere in the world, with at least a passable translation into their preferred language.
When access and language are removed as roadblocks, everyone can work together as if on a single project: all economic classes, all countries, all languages, nothing standing between us.
Yet we will still respect language and cultural differences. We can talk to each other without barriers, and we can work on shared projects where our goals align, but we will not force our perspective on others. We will still have many projects.
For example, there will probably not be peace in the Middle East in 2030. People will still disagree about "facts" such as countries, capitals, and borders. Within our projects, not everyone will use a single category system! But we are working together, respecting our differences, and being kind. It will be easy to "see an article in a new light" where that is appropriate, with tools that are symmetric (not unidirectional) so that big wikis can draw from smaller wikis and small wikis can draw from big wikis. The user experience reveals differences without letting these differences separate us.
Moving further, my dream is that all of the non-encyclopedia projects have grown up and out at least to the extent that Wikipedia currently has. Wikiversity is working on implementing The Diamond Age; Wikibooks are considered standard textbooks in many places; and Wikisource has reached par with libraries and archives in the same way that Wikipedia has reached par with Britannica.