Canadians, Chinese, and big guys like JP Morgan, Quicken Loans, and Ernst & Young are doing a lot of investing. What needs to happen is getting rid of excessive taxation and regulation so the little guys can get a piece. Its the only large city in the country that doesn't allow food vendors downtown.
Detroit is a major port city and the second busiest freight crossing on the continent. There is no "good" reason things shouldn't be booming.
Canada is paying to build a second bridge and that will ease the trade bottleneck.