A few years ago one of the most recent in a long line of Pop Art and Pop Art related exhibitions was being held at the Gemeentemuseum Den Haag. But since the mid Sixties numerous exhibitions have been held on Pop Art and Pop Art related artists. There were exhibitions at the Stedelijk Museum, Museum Boymans van Beuningen, Groninger Museum, Nijmeegs Museum, Kunsthal and the Gemeentemuseum and every time they were a huge success. My guess is that because the art is recognizable and because Pop Art established itself as a true mouvement in Art History, it has become popular to the masses.
Warhol, Lichtenstein and Wesselman are now household names and their works known by many. Perhaps it has even become to successful since images by these great artists are now part of Commercial activities and publicity campaigns which is a pity since these were not meant for being used this way. http://www.ftn-books.com has some nice duthc Pop Art publications available.