If it's not a unique disadvantage, do you really think it will affect sales? To overcome it I suppose they would need to find a more power efficient processor. MIMO is kind of a power hungry application what with the calculating a new spatial correlation matrix every few milliseconds. It would seem like the limitation will be universal to all other phones unless a phone manufacture buys some chip manufacturer with a mythical chip that solves the problem then keeps the tech to themselves.

>will it effect sales?

Sure it will: People will use it if it's there. If they don't put it in, people won't use it and will continue to laud the iPhone's battery life.