It only makes sense for them to do so if 4o is going to live up to OpenAIs promise. I would say that vapi is best positioned for this exact change happen which was imminent. Other companies like Air (that I believe will die soon) that have put themselves in the way of OpenAIs progress by not being transparent and developing their "own" llms. Vapi on the other hand does exactly the opposite and acts as a flexible platform for all of the available providers and with that not standing in the way of OpenAI but being able to ride their wave. This brings me to believe that Vapi is the most future proof unless OpenAI develops their own platform that allows for voice ai to be implemented into real-world situation and not just be a fun add-on to a chat-bot