I think tattoo art is still catching up with the rest of the art work - AT LEAST IN DIVERSITY (trying to head off the shitstorm of backlash, here). There is more and more variation in tattoo types. Dots. Abstract. Watercolor stylings. Whatever.
American traditional will always be the foundation here. Japanese and Indonesian will always be the foundation there - and crossovers will always exit.
Just like the rest of the art world, trends will come and go - and they SHOULD. It's part of the diversity of art in general, and helps keep things interesting.