The Dimensity 9400 is MediaTek's answer to the new Qualcomm Snapdragon 8 Elite processor for top-end Android smartphones. It is about to be supplanted by its Plus counterpart without particular delay - as early as March 2025, in fact, according to Digital Chat Station.
MediaTek's current flagship is composed completely of ARM cores (unlike the 8 Elite), the fastest of which is a new Cortex-X925. The 9400+ might have one too - albeit one clocked at 3.7GHz as opposed to 3.6GHz in the pre-existing chipset found in devices such as the Oppo Find X8 Pro (now starting at €767 in Europe via TradingShenzhen).
Digital Chat Station asserts that the latter will be found in more compact premium Android smartphones that focus on thinner sides and periscope zoom lenses as well as larger devices with more versatile rear cameras.
That prediction more or less tracks with what is guessed about the supposedly upcoming "Find X8 Mini" and "X8S", although the tipster hints that such devices might come from OEMs besides Oppo.