The point is, low end graphics are dying from the continued improvement from AMD and Intel, while high end stuff always comes out. So the same spec stuff is going to drop down in the series number code.
However, it could be nice if NVIDIA could set their products with just numbers, and add "GS, GT, GTX" to the improved versions, so we won't have to deal with Ti or Boost or "GTX 650 Ti Boost" Also, the improved GTX 660 could be something like the GTX 665. Seriously, Nvidia, you have one extra digit to play with. If you keep on refreshing the series like this, you are going to suffer at the near future when you need to replace the 900 series.