don't know about worldwide, but nationwide (US), there are about 74,000 people waiting for kidneys (another 23,000 waiting for other organs). I also don't know the counts for the number on dialysis, but I'm sure it's out there somewhere on the web.
www.UNOS.org (United Network for Organ Sharing) has really good data numbers that you can break down by state, region, organ, waiting time, and anything else you might want to know.