I'm not sure what projects you're talking about, but there is a long, long history of projects in this city (especially downtown), after having gotten approval from PAC and or city council, never seeing the light of day. Sometimes these projects will get resurrected several years later, but frequently they disappear into the ether.
It's hard to know what happens to these projects.
- Presumably in some cases investors can't be found, or disagreements may occur between investors and developers.
- I'm sure at other times market forces have a bearing and these can change between the time a project is approved and before shovels hit the ground. This happened to the first iteration of the Mapleton Centre.
- Sometimes a project (like an apartment building) will be greenlighted with the expectation that demand will eventually build enough to allow construction to proceed, only to be vanquished by poor demand, or increased competition.
- Sometimes a proposal is made just to be speculative, and in an attempt to create excitement in a vain hope to generate enough interest to finance construction. If interest is not generated than the project just vanishes.
At present, the project I'm most interested in seeing how serious they are about constructing is the Harper Building. I still give this less than 50/50 odds of proceeding.