That sounds very reasonable and of course it doesn't really matter, as it's inside the stadium is what matters most.If some company is going to pay £20m per year for naming rights, trust me they are going to be using every square inch of that screen. That screen will be no different than those on the inside (maybe not show game footage due to licencing reasons) but the screen will be dynamic, with adds and content from the club to keep eyeballs onto it and therefore exposure to those who have stumped up the money.
I do still wonder about the design choice though. Why not keep it as shown in the concept image giving said sponsor more square inch's for their buck?
I'm not OCD on this, just interested.