level cap is 70. this has been announced by Blizzard. go check on their site

Centaur can't go on the Alliance side as they are just pure evil creatures. they are the offspring of Cenarius' son and the princess you fight in Maraudon. Cenarius' son is the Keeper of the Grove (or at least just his spirit) you free after killing the princess. i'm guessing Maraudon is where the entaur were born in the beginning, thats why its a sacred place for them.

the Tauren were nomads because of the Centaur. if it weren't for Thrall, the Tauren would've all been wiped out by the Centaur in time.

a little story about Maraudon. the princess you kill is the daughter of Therazane the Stonemother, one of the lieutenants of the Old Gods.

no i didn't. but i read a lot from different sources bout warcraft lore.

Blizzard hasn't confirmed the new RACE. there won't be a new class. this was also confirmed by Blizzard. but they might change their mind in the future.
as for now, a lot of rumor hints strongly towards the Draenei as the new race for Alliance. i could think of no other race that could fit into the Alliance, even if Draenei being part of the Alliance doesn't seem right

i think the racial stats are quite ok. it sorta fits with the lore anyway. they should change the arcane resist on gnomes to something else.

i want 2 headed-ogres as the new Alliance race!

3. what has hating demons got to do with being Alliance? no demons on Horde side.
5. cows can wear humanoid armor. gnomes can wear humanoid armor. why can't furbolgs?
6. actually the hostile Draenei have gone mad as they have been cut of from their original world.
7. they number far less than the furbolgs. plus the furbolgs have all gone mad/corrupted. only ones left are Timbermaw furbolgs.

they hate orcs can be a good reason. but remember, they are allies to the blood elves as both races serve Illidan. Blizzard is going to change the story yet again if they introduce Draenei as the new Alliance race.

they weren't forced to ally. Illidan asked them if they wanted to help his forces in completing the same goal as them. so the Draenei allied themselves to Illidan's forces.

exactly why i said Blizzard is going to alter their lore yet again as they have already did so many times before.
did you know they never intended all these when they release Warcraft 1? they just wanted orcs and humans to fight. then they introduced a lot of background lore for Warcraft 3 to make the other new races fit in like they have already planned everything beforehand.

Murlocs won't be. Blizzard already released a look into the Murloc story recently. hinted that they may be tied to the Old Gods.

Timbermaw tribe no longer trusts anybody else for fear of them being corrupted and wiping them out. so they attack anything and everything they are not familiar with. to prove you want to genuinely help them you must help them survive, eg. killing rival furbolgs who have gone mad and threaten the Timbermaw.