I bred an Oldenburg hoping for just the same size you are. Mom - 17 hands. Dad - 16 hands. At 2 1/2 filly is 17.2. Uuuuuugggggg. (She is Contendro/Voltaire/Wellington for anyone who cares - because everyone told me that Contendro doesn't have any really tall offspring )
My almost 3-year old is about 15.2. Who knows where he may end up. Mom was 15.3 and never grew any taller after she hit 3 (but made up for that by growing WIDER). Dad was 17.2.
I'll be thrilled if he hits 16 hands.
My 2 1/2 y.o. is 17 hands at his rump & 16.2+ at his withers.
His full brother who will be 4 in March is 17.1 1/2+, this time last year he was 17 hands. He hasn't gotten much taller in the past year. When I bought him at 16 months old he was 16.1. Their dam is 16 hands and the sire, Hall of Fame, is 17 hands.
I have an 18 month old that should mature around 16.2-16.3 and shes 16 hands. I had a 2.5 yr old that sticked 17 1/4 at her inspection, I refuse to measure anymore, but I think shes stopped around 17.1. A gelding that should be around your desired height is going much slower and was 15.3 at 2 and slowly going up.
So really depends on the line, some like my 17.1 mare go up quick and stop, others may continue more slowly until 6, 7 or even age 8
I had a Dutch WB who was barely 16h at 2 and right around 16.3h when he finished growing UP at the age of 7 (though he continued filling out til 9).
Not a warmblood, but my TB gelding was 15.1h when I got him at 2. He stayed there until almost 4 and now at 4 1/2 he's sitting right at 16.1h and I expect him to reach around 17/17.1h based on both his string tests when he was younger and the fact that he still looks like a baby with LOTS of maturing left to go.
Jamie, I read on a yearling thread in the sporthorse breeding forum that on "average" warmbloods that grow to 16.2 were around 14.2 at 12 months.
Both of my guys parents are 16.2 so I'm keeping my fingers crossed he's at least that size when he grows up! He's very stout with A LOT of bone right now and vets say he will be a big boy. I hope they are right. Maybe since I since I see him daily that's why he doesn't look so big to me.