Top 500 Super Computers

At the top 500 website, I notice that the main CPUs are made only by four companies: IBM, Intel, AMD, and Nvidia.  HP was squeezed out in 2008, leaving only four players.  It makes me wonder if the trend toward fewer manufacturers will continue.  Also, the both the #1 super computer and #500 did not keep up with the general trendline over the last two or three years.  On the other hand, the average computational power of the top 500 has stayed very close to the trendline which increases by a factor of 1.8 every year.