Wow, what a buck! Very mature looking rack but his body doesn't look that old to me. Could be the angle of the picture.
Belly doesn't sag that much, no sag in the back, small brisket area, and no roman nose. Looks like an absolute giant of a 3.5 year old. Maybe he is 4 and I'm looking at the pic wrong.
I'm getting 140-144. You're right, if his 4's were longer he would bust 150 no problem. Still a shooter. He's mature, 4.5+. Once they hit 4.5, unless you have a record of them, the only way to age em is to send the jam bone in for testing.
I suggest you ground check him as soon as you're legally able to do so!