No, no. To be blunt, I'd like that for every race. I always was a little bothered, that even with enough races to begin with in vanilla, there always were these waves, during which you have more or less always the same aliens. First it's Sectoids, then the floaters begin. Then the Snakemen come, followed by Mutons and then the Ethereals. But not in a mixed way. More like 10-50 missions of a race one after another until there's some change. OK, sometimes paused by some Sectoids of Floaters, but in general, always big waves. Only in late game you begin to have some variety, where you don't have this likelihood of knowing, what's to come. Having more races probably spices it up, if they don't occur in this wave-like fashion.