Reproducing the table from the article with one extra column, the ratio of expenses to revenue for clarity, it looks like they're still operating with a very comfortable margin. Yes, the 19% margin is tighter than a 50% margin 12 years ago, and their existence depends on donations now more than ever ($23,463/yr is sustainable by a single engineer's salary, $65,947,465/yr is...not), but Wikipedia and other Wikimedia projects also serve a much wider audience and broader purpose. This isn't scary in and of itself, especially if they've got cash reserves to give them time to tighten the belt later on if it becomes a problem and someone in a leadership position is monitoring their finances to act if their burn rate gets too high... I've seen plenty of nonprofits with tighter margins survive and succeed.
Year Revenue Expenses Net Assets Expense Ratio (1-margin)
2003/2004 $80,129 $23,463 $56,666 29%
2004/2005 $379,088 $177,670 $268,084 47%
2005/2006 $1,508,039 $791,907 $1,004,216 53%
2006/2007 $2,734,909 $2,077,843 $1,658,282 76%
2007/2008 $5,032,981 $3,540,724 $5,178,168 70%
2008/2009 $8,658,006 $5,617,236 $8,231,767 65%
2009/2010 $17,979,312 $10,266,793 $14,542,731 57%
2010/2011 $24,785,092 $17,889,794 $24,192,144 72%
2011/2012 $38,479,665 $29,260,652 $34,929,058 76%
2012/2013 $48,635,408 $35,704,796 $45,189,124 73%
2013/2014 $52,465,287 $45,900,745 $53,475,021 87%
2014/2015 $75,797,223 $52,596,782 $77,820,298 69%
2015/2016 $81,862,724 $65,947,465 $91,782,795 81%