if your guild had 12/12 in cata and you buy the mount and use it but you get kicked(or leave) will you then lose your mount?
no, google the answer next time. move along
You shouldn't lose the mount, I didn't lose the Guild Page or Armadillo companions, nor the cloaks. Shouldn't be much different for the mount
It's been discussed in other threads too, you won't lose anything you earn while you're in guild, doesn't matter if you leave it yourself or get kicked, you won't lose anything you bought.