I'm thinking technically just the slides, bathrooms, and one restaurant has to actually be done. Theming, horticulture and finishing touches may lag behind after opening but won't keep them from being able to open. We've already seen people using some of the slides.I'm still having a hard time seeing them get this done in time. We're almost at the point of counting down by hours and there's still a lot of work to get done.
The way I look at it, there's never a guarantee that all rides will be open opening day. Take Universal Florida in 1990 for an example. Kong was hit or miss, JAWS was closed for months, and BttF wasn't even fully built yet, just had a sign that said coming soon. They're gonna open, with or without all the rides I'm sure.
Personally I'm impressed by how much has been accomplished in just the last two weeks alone. Really blowing me away.