Historically speaking, the Pro/Max versions of the chips have become available at around the same time the next-generation base chip does. So, M4 Pro/Max shipped when M5 shipped, M5 Pro/Max shipped when M6 shipped, and so forth.
The M7 generation is said to be another huge advance on local LLM performance, so Apple is skipping the M6 Pro and M6 Max to bring out the M7 generation early.