This report was presented at the Wikimedia Monthly Metrics Meeting last week and mentioned in the latest issue of the Wikimedia Engineering Report.
We conducted a thorough review of traffic data and trends and confirmed a downward trend in desktop pageviews in 2013. This trend is not reflected in desktop unique visitors or mobile traffic. We are working on complementing pageviews with other traffic metrics that will help us better monitor readership trends. We engaged with external parties (Google and comScore) to obtain data about referral and mobile traffic respectively.
The report is also available direct from Wikimedia.