1) Free market apartments: with tenants not having to pay broker fees up front, LLs can and will come up with workarounds. E.g. 'move-in-fee' of 5k or a 'move-out' fee. They will be able to charge more, especially on renewal leases.
2) Rent regulated apartments: LLs can't play those games, but they can say 'only available if you hire such and such a broker', or they might only list the apartments on a website that operates on a subscription basis where they get a cut somehow. Or, at the margins, this is a significant cost for money-losing units, so they might just add those units to the list of units permanently off the market.
I do expect brokerage fees to decline somewhat, and this may affect pricing for streeteasy and zillow and the other advertising portals, but this is not going to be a huge change, and is going to hurt a bunch of low-income tenants.