i think it might turn out win-win, but maybe i'm being optimistic. on one hand, you'll have regulated trading with full KYC through a more traditional broker-dealer relationship. regulators are happy, accredited/institutional investors are happy, broker-dealers are happy.
on the other hand, since we're talking about securities tokenized on decentralized platforms, you can likely invest into said securities on secondary/p2p markets and avoid regulated broker-dealers entirely.
fully regulated markets bring thick liquidity, and arbitrage opportunities will probably incentivize some of that liquidity to spill over into the secondary/p2p markets.