First congratulations with the launch of Wikistats 2! A major milestone!
As said in the launch statement, migration of (part of the) existing reports will happen over time. Is there a road map, with timing and priorities?
I fully expect that migration will be incremental, not a big bang. I just browsed the survey  to remind myself which reports are in highest demand.
There is a handful reports with 30+ votes (the numbers in the TOC are indicative, but manually maintained).
Here is my suggestion for which cluster to tackle first, and why:
Most prolific contributors , and variations on that (bots, absentees, ip addresses), deal with individuals.
Migration into to one combined and dynamic Wikistats 2 report would probably garner a lot of attention, and open up such metrics for many more users.
I'm not sure what other existing reports outside Wikistats already provide part of functionality. There are a few.
But maybe not as comprehensive and condensed as the report in Wikistat1.
Idea to bring this further than Wikistats 1's implementation:
On top of presenting the top 50 (or maybe 500) in a (scrollable) list, it would be nice if people can also query by user name.
A user might enter filter criteria like 'content namespace, or all namespaces' / 'period all time or last year'.
Another nice addition would be to link per listed user name to a second query which retrieves stats for all wikis for that user, say ranked by number of edits.