Four years doesn't sound that unreasonable to be fair, Tottenham's has been three years in the making and they got to make a start before they had to knock the old ground down, having to demolish the existing ground first is going to add a big chunk of time to the programme. The nature of the site will make it a pain in the arse too, blocked in on all sides, only two points of access and they're from a fairly small road, railway all down one side just for added complication.
Wasn't there a new connection into the underground station too? Think it was an elevated walkway that came round the back towards the railway line to save everyone having to filter out onto the street and queue up outside the station into the road. Further work to add to the time and costs.
I still think he's playing face as much as anything, things not going his way with the Visa so pulls a big investment, bye bye cash and job opportunities and everything else that it'd create. If/when his Visa/residency is resolved I imagine the development will magically reappear on the agenda.
