As of now, there doesn't seem to be any news of new High School DxD manga being produced. Usually, such information would be shared through official channels or fan communities, but nothing has come up yet.
In a Naruto and High School DxD fanfiction, there could be a scenario where the protagonists of both stories meet in a neutral dimension. Issei from High School DxD might be intrigued by Naruto's ninja skills and determination. Naruto, in turn, could be curious about Issei's Sacred Gear. They could start training together, sharing their knowledge and skills, and ultimately have to face a common enemy that threatens both their worlds.
One possible fanfiction could be about Naruto characters attending the school in High School DxD. For example, Naruto's positive and determined attitude might clash with the more complex social and power dynamics in the DxD world. He could make new friends or even rivals among the devils, angels, and fallen angels.
One idea could be that Ben Tennyson somehow gets transferred to the world of High School DxD. He has to keep his alien forms a secret while dealing with the devils, angels, and fallen angels in the school. Maybe his Omnitrix could be misinterpreted as some kind of powerful devil device.
One possible fanfiction could be about Naruto characters somehow ending up in the world of High School DxD. Maybe Naruto's skills in combat and his determination would make him a formidable opponent in the battles that often occur in the High School DxD universe. He could form interesting alliances or rivalries with the characters there.
A fanfiction could focus on Naruto's training regime influencing the characters in High School DxD. His intense physical and mental training could inspire the students at the school. They might start incorporating some of his training methods, like running up trees or on water, to improve their own strength. And Naruto could also learn from their magic-based training and combine it with his chakra control for new and powerful techniques.
A fanfiction might explore how the power of the Excalibur in High School DxD would interact with Naruto's chakra. Since the Excalibur is a powerful holy weapon, it could have some interesting reactions when in the presence of Naruto's unique chakra, which is different from the magic in the High School DxD world. For example, it could either enhance or nullify certain abilities depending on how the author writes it.