Very possible. Every previous generation has had two GT games whereas this one will likely have just the one with GT6 being saved for the PS4 if Sony knows whats best for them. Its also possible that Halo: Reach will exceed the LTD sales of Halo 3 by a reasonable margin given the fact that all things point to it being a much better game and theres less FPS competition this year. So all things considered GT5 could sell more than Halo: Reach even if Halo: Reach sells more than Halo 3 or the other way around. Given the fact there are very few 10 selling franchises out there it makes it exceedingly hard to predict how things might or might not pan out.
Tease.