Currently, it adds an iframe to tools.wmflabs.org/wiwosm which is not of production quality and violates our privacy policy.
Current usage is MapSources template on most Wikivoyages, and a single page on dewv.
We need to figure out the precise way to replace <slippymap> in templates (example) and discuss it with community. The actual replacement would not touch too many pages and thus should be fairly straightforward. After that, <slippymap> should be removed completely.