It seems to me that, until UT Austin catches up with Stanford and Berkeley in its ability to churn out tech talent, we can apply Betteridge's law of headlines here (i.e. "Any headline that ends in a question mark can be answered by the word no.").
If anything, the biggest threat to Silicon Valley's dominance seems to be the post-COVID trend of remote-friendly tech employers. That has already benefited Austin, but not exclusively so.
EDIT: Xerox PARC apparently shouldn't be included in that list. Its founders were Jack Goldman and George Pake, neither of whom were alumni of the companies or universities I mentioned.