My general expectation is for USD Price floor to rise inversely as block reward declines
This is correct.
But DNM's likely will stick to BTC out of inertia. Most DNM busts have nothing to do with blockchain analysis. It's all sting vendors and controlled deliveries.
The reward factoring may be a wee optimistic, as global energy priced in USD declines. I suspect recent BTC repricing was mosttly attributable, and the bfx margin calls merely symptomatic.
"Most", however, is telling. It wouldn't take more than one, strategic, bust to start a stampede. And it has already been a factor in some. And it will inevitably be a factor in many more.
Similarly, a prominent Chinese execution for economic crimes in the form of blockchain-based capital control violations, if it occurred in close proximity to even momentary public awareness of XMR could suffice to redirect some relatively large flows.
That this sort of thing has not already become a significant valuation factor can be explained: Firstly, there are just too many entrenched alternatives in place for evading capital controls, albeit accessible only to large established players, and execution rates quite low for crimes associated with adequate stealth and wealth to make bribery feasible. Secondly, the appeal of the channel depends on liquidity, a bootstrapping problem, and so much as access to liquidity is mediated by BTC the benefits for avoiding vulnerability to blockchain analysis lack credible, pragmatic value.