Heya,
For the current uses of the airfield, I do not see the immediate need for an extension,
AFAIK there are no performance limitations which would affect the airfield at the moment.
What I think they really need to look at is the taxiways & apron areas. They are dodgy at best. Whatever new stands we get will be good news and hopefully relieve some of the PPR requirements that are very strict at Exeter.
A full lenght taxiway would be nice too, would increase the number of movements possible.
With the new stands, and the removal of the grass apron, all GA is being moved northside which is good as it no longer requires them crossing the runway at C to taxi down F.