Originally Posted by blue eyed pony
I severely doubt it to be honest. My filly is 13.2 at not quite 13 months and she'll be lucky to hit 15hh. They're 90% grown by 12 months and 95% by 18 months. You MIGHT, with correct nutrition, help her grow to around 14hh but I don't think she'd go much taller.
Maybe with ponies this is correct, but the slow maturing breeds will often shoot up as much as a hand, after turning 2.
My hanoverian nearly 15 month old gelding, is 14.2hh at the bum, and 14.1hh at the wither (going through bum high growth spurt again!) - his sire is 17hh, and dam is 16.1hh. Sire throws quite big, usually over 16hh at least.
If your assumption was correct, my yearling won't be more than 15hh - but at the rate he is currently growing I'd say he'll hit 15hh pretty soon!
My coaches old hannoverian mare was only 15.2hh as a 2 1/2 yr old. At 6, she was 16.2hh. Go figure!