4 Japanese fleet carriers sunk in one day. Kaga, Akagi, Soryu and Hiryu. 4 June 1942 was the death of the IJN.
I don't know what would have happened if the Midway came out differently. I guess the final outcome would have been the same, but it might have taken longer.
Almost the death of the IJN...they still had enough to kick our butts at Savo Island a couple of months later, and continued to make life tough for another six months to a year, but...I do think Midway spelled doom for japanese military aviation.
They continued to throw their best pilots back into the meat grinder until they were all gone. We rotated our best pilots out, and over time, that was the difference.
Even as early as the battle of the Eastern Solomons or Cape Esperance, gunners on ships noticed a clear change in the quality of the Japanese pilots they encountered, fighters, bombers and torpedo planes. Earlier in the war, they had been tenacious and good. They became, even that early, much less persistent and noticeably less capable.
Fortune was in our favor on this day.
Good fortune, and untold bravery.