So was this in roadmap before but than they had deleted it? It looks like very strange... Seems they can't launch exchange or don't want anymore. Or may be they have some legal issues with this

STE is and has always been the whole point and goal of Dusk because it's build to run it. STE running on Dusk is also mentioned in the Bitfinex - iFinex whitepaper (i am not sure if bitfinex broke the nda by publishing it because the dusk team is silent about any details about their partnership on this).
Dusk has just removed timelines because schedules are harder to keep then they thought. And to be honest that i can believe. The amount of regulations they have to meet for this must be insane, and i would be surprised if the legal issues weren't the main hurdle that's slowing the process.