Looking for Adult LEGO
Yes. LEGO® may still be a toy, but it clearly a toy for all ages.  Here are two examples:

LEGO Architecture

LEGO Architecture is clearly aimed at adults. 



From one of LEGO's press releases:


  With models developed in collaboration with architects, LEGO Architecture inspires future architects, engineers and designers as well as architecture fans around the world using the LEGO brick as a medium for reproducing esteemed structures. Fans of all ages can collect and construct iconic architectural sites, including: Frank Lloyd Wright’s Guggenheim Museum and Fallingwater, the Space Needle in Seattle, the Willis Tower and John Hancock Center in Chicago, New York’s Empire State Building and Rockefeller Center, The White House in Washington, D.C., Farnsworth House in Plano, Illinois and the Burj Kalifa in Dubai. Each LEGO Architecture set contains a booklet featuring step-by-step building instructions that is prefaced by exclusive, archival history, information and photographs of each iconic building, its design origin, its architect and its architectural features.


I'm sure there are some young architects out there, but this level of depth is more typical of adults.



Serious Play

LEGO has also a corporate-focused play for adults called LEGO® SERIOUS PLAY®


  Build a better workshop with the LEGO® SERIOUS PLAY® program!
  
  The LEGO® SERIOUS PLAY® program is a radical and innovative process designed to enhance business performance through building with LEGO bricks.