Web Logs ("Blogs", as the kids call them) will become so prevalent a means of communicating that there will eventually be no other new content. Instead, blogs will endlessly comment on other blogs, which themselves comment on other blogs.

Manufacturers will continue to make electronic devices smaller until a child chokes on one. Then they will place a warning label on the box and continue.

We will reach a point when, like copyright laws, retirement age continues to be increased faster than people age. Specifically, a child born after 2550 will never be allowed to retire. Also, due to continuing advancements in medical science, that child will be immortal.