From the USGS: "The U.S. Geological Survey (USGS) has stopped acquiring images from the 27-year-old Landsat 5 Earth observation satellite due to a rapidly degrading electronic component. Landsat 5 was launched in 1984 and designed to last 3 years. The USGS assumed operation of Landsat 5 in 2001 and managed to bring the aging satellite back from the brink of total failure on several occasions following the malfunction of key subsystems. There is now an increasing likelihood that the Landsat 5 mission is nearing its end. […] For several months, the Landsat flight operations team has been closely tracking the fluctuating performance of an amplifier essential for transmitting land-surface images from the Landsat 5 satellite to ground receiving stations in the U.S. and around the world. Over the past 10 days, problems with the amplifier have led to drastically reduced image download capabilities, a sign of impending failure. […] Landsat 8, currently called the Landsat Data Continuity Mission, is now scheduled to be launched in January 2013."
We obviously mentioned Landsat 5 often in the past, including in 2005, 2007 and 2009 when it suffered technical problems, but each time, was able to resume satellite imagery acquisition. This time, it's probable it's really the end of Landsat 5. Here's the Landsat 5 Wikipedia article.