They haven't done much around Emirates? Haven't they put in a load of new transport links? Surely that will lead to a lot of private investment in the area when markets improve?
Nope. There's still the Arsenal and Holloway tubes, which were always there. There's Drayton Park station which was always there, but doen't run at weekends. They've spent a lot of money on the overland from Highbury to Stratford, but that was all from Olympic money, and they've upgraded every station on that route, not just Highbury & Islington, so I'm 99% sure that wasn't connected at all.
The old ground always sat in a pretty posh area of North London, the new ground is a stones throw, but moving towards a poorer area. There's no discernable difference in that area since the new stadium was built.