Yes, the more I think about it, the more this seems to be the only logical trade-off. I personally still can't see any other. One single port will I am afraid cause quite some frustration, and my guess is that choice will cost Apple a little on sales. I don't think they made such a decision lightly. But I can see them going with one if a second port meant a fan: thickness, most likely, weight for sure, and battery life would be quite affected by that.

I'd be really curious about the Surface 5, in this regard. I am sure it will come in some flavor to compete with the new mb (Core M), so it will be interesting to see its design in terms of ports and fan.