Ok rant time, also known as theoryHammer.
The eldar can't win on grounds of they do not have the numbers needed to launch a war of this scale.
Chaos daemons the same, the greater gods are greedy and every daemon they spawn leeches a portion of their power away. Yes khorne could spawn a billion bloodletters but he would cease to be, khorne being a god and all, will never do that. On top of that when/if the eldar and humanity die out, the chaos gods battery of power will be gone, this will almost utterly decimate deamons as well as...
Traitor Marines have the advantage of extremely long lives 10,000 years of real time experience, which makes for a deadly warrior. the problem is again numbers. Even with the original traitors and all the individuals that have gone rouge since the heresy, chaos marines die of at rate much to high for decent growth. Hell khorne's realm is a battle field, that tens of thousands fight and die by the day for his favor.
Humanity, as much as id like to say would win, is much to fractured to take it all, but it is much to numerous to fall completely. a single message sent out across the segmentums, would marshalize humanity into the single most formidable defensive bastion ever. "The emperor is in danger!!!" would bring every single marine, sister, inquisitor, guardsman, and titan to the sol system. And if they are still alive Dorn, Russ, the Khan, and the Lion would come back and Guilleman would be brought out of stasis. With all of this Terra will never fall, we wont be ale to leave system, but it wont fall.
Which brings me to the last four. Crons, orks, nids, and tau.
Tau have hooves, things with hooves are called live stock. Live stock is for eating, the tau just haven't realized that they are actually quarter pounders yet.
The crons will eventually march upon galaxy extinguishing all life, just warping out and coming back with more number win it gets too bad. The problem is nids and orks eat there foes, and I don't believe digested cron will warp out of an ork gut.
and lastly the eternal stalemate that will rage across everything, and it is simple orks spawn all they need is sunlight to grow, they are after all mushrooms.Which provides the nids the equivalent to a self refilling all you can eat sizzler buffet. orks get bigger and spawn more orks, they kill nids, nids kill orks, nids make more nids from the ultimated food supply, orks spawn more orks.
So in the end Orks and Nids will be EVERYWHERE except sol and All three survivors will never make any real head way again.
BLOOD FOR THE BLOOD PRIMARCH!!
SKULLS FOR THE GOLDEN THRONE!!
WAIT A SEC. . .