I have a problem with this whole "hybrid" theory its such crap; im sorry but if you read the history behind the toss and the zerg, the protoss were given purity of FORM, and the zerg were given purity of ESSENCE. if the two races were combined the race would be unfairly powerfull blizzard would NOT put that in their game, second off, it never said the terran were combining toss and zerg, they were experimenting with zerg genetics, im sorry but 1 zealot could waist 2 marriens what makes you think thay could actualy catch a toss to expirment on?
if there is a new race it will more than likely be another creation of the xel'naga, because it never said why they left there homeworld, yes the zerg wiped out all the ones that were HERE, but theres probubly still some there, and if you read the history thingy, it says "they expermented on many races, most of wich were failures..." so there are OTHER races the xel'naga were expermenting on..
if there is a new race I hope it will be a non-humaniod species, i think that would add some more variaty to the game, maybe a race of subteranian ability? the posiblities are endless...