Hard to imagine anything worse than LaTeX for web layout. Imagine resizing a page and waiting for the re-compilation of the whole page.
The reason why I consider it a possibility is that LaTeX has two things out of the gate: The technical capability, and a small but arguably rabid user base. It's the sort of thing that can take an early lead but is quite unlikely to sustain it.
But you can't deny that LaTeX has had incredible staying power, despite the list of issues that everyone who uses it has with it.
Now if only the browser conglomerates can disrupt Pantone too...