Outside of the limited medical program, the purchase and sale of cannabis are not legal here on an adult-use basis. Although it is legal to possess or gift cannabis, there is no actual adult-use industry.
Many stores will "gift" you cannabis if you make a qualifying purchase, but these stores are far from acquirable or financeable. A recent bill was proposed to ramp up enforcement against the District's unregulated cannabis businesses, but the votes fell one short in needing to pass. The program is as ass-backward as they come, but for now, if you find the right store, you can pay $10 for a sticker and walk out with a dime bag.
There is no notable activity at this time.
The US Congress governs Washington DC, which speaks for itself. Look for change at the federal level before there is real market opportunity in the District.