Nkrumah's one party state and President for life powers were something that was bound to catch up with him at some point because of the amount of power concentrated under himself making it tempting for any colonel with ambition to try to do something. His 1964 North Korea-esque referendum was probably the beginning of the end, however, and his regime might have hung on had he been less ostentatious with his international and PanAfrican ambitions.
The longer term impact would be the continual inflation of the Ghanaian Cedi under his leadership as he went ahead with his nationalization programs, and a more severe brain drain than in OTL. The Trade Unions Council that he sought to make a pillar of his rule turned very quickly against him after the coup, perhaps pointing to an issue in the ideological commitment of some of his subordinates to his ideas. However, he would likely continue the cult of personality aspects that would garner him substantial rural support and make his regime a lot harder for the military and professional classes to challenge.
The big questions, of course, are whether the inflation that would have continued would have been bad enough to sap away at the living standards of the urban industrial working population. If so, he would have trouble coup proofing his rule; if not, then maybe things go differently.
As he slid further and further towards the Eastern Bloc, I would expect economic assistance from the UK and US to dry up completely, as it was trending in OTL towards (the fact that his regime's ouster was known to be in the docket sped this up as well).