True. If they’d rotated their veteran navy pilots home after the middle of ‘42 to train cadets they could’ve been a more potent force for a longer period. As it was they lost most of them by the end of the Guadalcanal campaign.
Ironically, the last three ships sunk at the battle of Midway were on June 6, exactly six months from the attack on Pearl Harbor. One of them was the Japanese heavy cruiser Mikuma, sunk by American carrier based bombers. The other two were the disabled American carrier Yorktown, and escorting destroyer Hammann sunk by the Japanese Submarine I-168, which had managed to slip through the destroyer cordon with other debris from the battle. The Yorktown managed to stay afloat until the following morning when it was abandoned after further salvage efforts were deemed hopeless and slipped beneath the waves at 0500 hours, almost the very hour that the first Japanese carrier based planes had taken off for the attack on Pearl Harbor exactly six month earlier.
Yamamoto's words could not have been any more prophetic. And, of course, Yamamoto himself was also gone shortly after the Guadalcanal campaign ended.