Never mind that bookstore sales have been declining all year long: Reuters correspondent Justin Grant has gotten hold of Book Industry Trends 2007, which leads him to conclude the publishing business doesn’t need Harry Potter to succeed. Specifically, the net revenue for American publishers in 2006 increased by just over three percent to $35.7 billion even without a new J.K. Rowling book, and the Book Industry Study Group expects that number to hit $42 billion within the next half-decade. (Unless, that is, kids today prove to be incredibly shallow and abandon reading to play video games.) Standby industry analyst Albert Greco dubs the book biz “stable with modest growth” and “healthy even without Potter.” Now if the bookstores could just figure out a way to share in all that bounty…