The current pace is no different than what it has taken from groundbreaking for pretty much anything Disney has done this century, so there's no reason to not just enjoy the progress.
Of all the recent attractions built at WDW, Avatar is on track to have taken the second longest, and may the longest. Yes, Fantasyland took longer overall, but I believe if they had not decided to substitute the Mine Ride late in the game it all would have been done in under 40 months.
Avatar 1/10/2014 4/1/2017(?) 40
Frozen Ride 10/5/2014 6/1/2016(?) 20
Toy Story Third Track 9/25/2014 5/24/2016 20
BatB/Little Mermaid Section of FLE 2/10/2010 12/6/2012 34
Storybook Circus 2/11/2011 9/30/2012 19
Mine Ride 9/1/2011
4/30/2014 31
Tangled Restrooms 5/10/2011 3/8/2013 22
Expedition Everest 6/1/2003 4/7/2006 34
Mission:Space 3/29/2000 10/10/2003 43
Test Track 1/2/1996 3/17/1999 38
Test Track Presented by Chevrolet 4/15/2012 12/6/2012 8
Toy Story Mania 11/18/2006 5/31/2008 18