Kieboom had an OPS+ of 72 this season, an OPS of .619 to go with his .207 average, 62 strikeouts in about 60 games and 250 plate appearances. He hit .236 with a .760 OPS at Rochester. If that makes him a proven AAA hitter, then let him stay in Rochester. Of course he should be invited to Spring Training, along with Jake Noll and with a player to be found later who is at least a mediocre major league hitter.
Kieboom cannot hit major league pitching. He has demonstrated that. If a miracle happens and, somehow, he can hit in the big time, that's nice. My all-time favorite third-baseman did not make it until he was 23, although that guy only had two seasons in the minors. Then he had an OPS of .870 and an OPS+ of 137. He was a crude third-baseman, but if Kieboom could break through like that we would all be happy.