Hooded,
In all honesty, I don't think a runway extension is on the cards. I think the story arose because the recent government white paper on aviation noted there was space to extend the runway, but I can't realistically see this being needed. Peel Holdings are spot on IMO in identifying the road layout and terminal as the immediate priorities.
I think Peel are a pretty shrewd crowd who know what they're doing. As I said, Teesside will always be the junior airport of the region, but it's still the de-facto airport for several hundred thousand people in the immediate area plus large parts of County Durham and North Yorkshire. I think Peel recognise that MME has underperformed for a long time, and that with better marketing and some investment in the airport itself, there's scope to exploit this potential market more effectively.