Although Yorktown's air group was cobbled together from Saratoga's squadrons and its own VB-5, there was no attempt to board a deckload of other squadrons because there were none available - Lexington's had gone down with her, and Enterprise's and Hornet's were on their respective ships. The closest example I can think of, at that point, was when Hornet carried the Doolittle B-25s while her air group was hangered - Enterprise furnished air cover until the bombers' launch. As has been mentioned, I think just 2 Japanese carriers would've been sunk the morning of June 4 (Kaga and Akagi would've still been sunk by Enterprise's bombers but Soryu, which was sunk by Yorktown's, would've escaped under this "what if"). So, Japan's counterstrike the afternoon of June 4 would've consisted of planes from Soryu and Hiryu, resulting in at least one US carrier sunk, and possibly the other as well because the Japanese strike force would've been doubled (and would've faced a smaller CAP). We can assume that Hiryu would've sunk the afternoon of June 4 only if we assume that Enterprise escaped the earlier Japanese counterstrike (Hiryu was struck by a combined Enterprise-Yorktown force). If we assume just one US carrier lost, it would've been a wash because Yorktown woud've been available for service after the battle; if we assume 2 carriers lost, that would've had repercussions in the Solomons later. And if Hiryu wasn't sunk under this "what if", it would've increased Japan's force available in the Solomons.