Let us assume then that the Japanese first wave against the US carriers would have taken out the Yorktown the first time (four carrier strike groups instead of one). Lets further postulate that the Enterprise and Hornet, with their torpedo squadrons savaged in the first attacks, fail to sink any of the Japanese carriers and soon follow the Yorktown to a watery grave.
Blackfox5 beat me to it, as I was going to start off with the Solomons islands campaign as well.
I would think that the US, down 4 carriers in two battles (and the Japanese being correspondingly up by four carriers that they historically lost but retain ITTL) is going to have to forgo offensive operations entirely for at least a year, which means that the Japanese are going to have a free hand in continuing their southeastward advance from the Solomons. With land based air entrenched on the south pacific islands, I would be surprised to see new guinea or new Zealand not being taken before the US can do anything about it.
Also as blackfox5 pointed out, this will mean that the Japanese are going to be able to throw far stronger forces into the Indian ocean, as they will not only still have the four carriers they historically lost at midway, but they are not going to be having to counter any US offensives at all.
One thing I disagree with in Blackfox5's post however is, the idea of a ground campaign in India. Would it not make more sense from the Japanese point of view to simply take the islands at the entrance to the red sea and slap down some good land based air to close the Suez/red sea to allied shipping? send some submarines just for spice, and the Indian ocean is going to become a far more costly theater for the allies. Far less manpower needed for this than jumping headfirst into yet another full fledged ground war in one the the most densely populated nations in the world (at the same time as they are already fighting in China). Also, what if they were to take and garrison parts of french Madagascar? I would think that subs and land based air there could cut off allied merchant shipping in the Indian ocean entirely. And this could lead to some major repercussions in the ground war in China, as there will be no allied reinforcements and supplies being sent 'over the hump'.
All in all, this would have extended the war with Japan by at least two years, and perhaps as much as five (assuming the worst --- Britain sue's for peace w/Japan, and Japan conquers China), this would mean that Japan is hit by an American nuclear bombing campaign in 1947-1950.
Just my two cents worth.....