I find myself wondering if the Tango is selling significantly better than the Salsa. Aside from a slight difference in shape, I'm pretty sure the two toys are almost identical in terms of function and power. If one of two nigh-identical toys is the better seller, they may be thinking, "Hey, why bother making them both?"
That's just speculation on my part, though, and it still seems like a strange decision. The best bet would probably be to email the company and ask them. I personally like the Tango just fine, so I personally don't see it as any big loss, but I feel bad for those of you who really liked it.