Focusing on correctness and security isn't as popular or sexy as having the latest and greatest bleeding edge superfast stuff, until that stuff breaks and leaves your data vulnerable. But that's unpleasant, so it's easier to deflect than it is to question whether your goals should be adjusted.
That's not anywhere close to a prediction of Meltdown. Meltdown is a side-channel attack that can cross the user/kernel boundary. What Theo was predicting is that all chips are getting complex MMUs to the point that there are bugs in corner cases that could be exploited to create infiltration leaks. Side channel attacks aren't bugs, insofar as no one is really promising that you can't observe side channels.
But the observable out-of-order execution used by these chips that led to Meltdown is a bug. Proof: AMD chips aren't affected by it:
> The Meltdown vulnerability primarily affects Intel microprocessors,[52] but some ARM microprocessors are also affected.[53] The vulnerability does not affect AMD microprocessors.[19][54][55][56] Intel has countered that the flaws affect all processors,[57] but AMD has denied this, saying "we believe AMD processors are not susceptible due to our use of privilege level protections within paging architecture".[58]