I theorize this is what will happen in the next update during the FOG maintenance. Knowing Inoda, he'll most likely pester Asuna about her killing him in the game. Ergo, she'll most likely give in to his request by givin him a handjob, letting him fondle her, or something minor along these lines to further break down her IRL sexual morals.
I'm also in the camp of Suguha somehow being the spark that leads Asuna to have no guilt about cheating on Kirito IRL. But I'm honestly kinda hoping for Sinon to be the catalyst. My wishful thinking is that Kirito needs to make a decision between helping Sinon or Asuna and will instead help Sinon. After helping her, Sinon visits Kirito at his apartment to thank him and decides to return the favor by sleeping with him, as she probably believes that her only worth is her body. Asuna makes a visit to his apartment without letting him know ahead of time to ask about him flaking on her. She walks in on this without being discovered, leaves, and decides to go all in on Inoda.
I hope this happens, as I feel Sinon has been underutilized in terms of sex scenes, and IMO, seems like she's gonna be written into the "trying to sleep with Kirito" party after he helps her with her revenge against Hebishima, furthering Kirito's degeneracy.