Wikitree reports on its front page that there are 327,390 genealogists on the site contributing to 11,263,674 profiles as of May 5th. I have made the top 1000 contributors list two months running; I am 465th in the April 2016 club 100 and 726th overall for April 2016. I estimate that I have contributed strictly fewer than 100 profiles in the two months I have been contributing; the contribution ranking statistics would seem to suggest that the contributors below me in rank have probably contributed a similar or lesser number of profiles to WikiTree.
Based on that, I would infer that almost all genealogists are contributing less than 50 profiles on average per month. From the database dump statistics, we can actually find an average number of profiles per month based on the increase in the number of profiles.
209,678 profiles were added between April and May. 209678/327,390= 0.64 profiles per month per WikiTree genealogist. If I am representative of the Club 100 contributors then I would expect that Club 100 contributors add on average around 10 profiles per month, and I would expect that Club 1000 contributors might add on average 100 profiles per month; there are 261 Club 1000 contributors and 1382 listed Club 100 contributors. In total, there are 1643 genealogists in the Club 100 or Club 1000 contributor list shown which is 0.5% of the total listed number of genealogists on WikiTree.
From this, I would think that the vast majority of Genealogists are inactive and the vast majority of profiles added are due to genealogists not in the the Club 100 or Club 1000 contributors list. The top Club 1000 contributor has 12,197 edits which I expect translates to around 1200 profiles or a maximum of 12,197 profiles in a month; there are nine Club 1000 contributors who have contributed in excess of 5000 edits with almost all Club 1000 contributors contributing significantly fewer edits than that. Even with the prodigious output of the top 9 contributors, the vast majority of edits would have to come from the other 99.5% of editors.
Growth for WikiTree then comes more from new people joining and adding at least one profile; the effect of dedicated genealogists contributing massive amounts of profiles relative to other genealogists is unlikely to contribute significantly to the overall growth of WikiTree.