We may never know, there may not have been any solid guarantee, or whatever version of a guarantee may have existed at one point may never be realized in exactly the form in which it was conceived. Whichever of those things is true, I think it's entirely likely that the city won't feel especially beholden to waterfront transit pledges, and the developers that have bought land or already built in this area don't really have any recourse.
If you look at the discussions surrounding the 15-year priority transit measures, "waterfront transit" has sort of always been thrown in as a bit of an afterthought (at least by my reading). There are clearly much higher-priority transit projects that have a far greater degree of political buy-in, and even those don't have complete funding plans.
It could be a very long while before ground is broken on a waterfront LRT (unless that winds up consisting of a regular Flexity streetcar line extension, which could be faster, but even that would of course need a funding plan).
As someone said up-thread, though, there's not really any definitive indication that those dynamics have hindered residential (or commercial) sales in the meantime. If that were or becomes the case, it might actually provide a bit more fodder for developers and other stakeholders to hold up to the city as evidence for the need to get moving on transit for this area.