Given the scale of the global COVID-19 crisis, and particularly the French government's rather robust response, it was only a matter of time before running this year's Festival de Cannes in its normal slot became untenable.
So at present, the Festival de Cannes, Marché du Film, plus the three official sidebars (Directors' Fortnight, International Critics' Week, ACID) will not go ahead as planned. Those who've already paid for market accreditation should contact the Marché du Film to request a refund.
Interestingly, unlike other big festivals (e.g. SXSW) which have just cancelled their 2020 editions outright, the powers that be in Cannes HQ have suggested the event could still run in 2020, perhaps in late June or early July.
This is probably wishful thinking. It's likely the health risk and associated lockdowns will have dissipated once the northern hemisphere summer is in full swing, but the world will still be reeling from economic fallout. Confidence in the markets will probably not have returned by that point, and companies which have weathered the storm will most likely still be in the process of picking up the pieces. Not to mention seeing who's left standing in the airline business.
In an effort to try and mitigate some of this, the Marché du Film has announced it will run a 'virtual marketplace' during the original festival dates. In partnership with Cinando, the Market will offer online screenings (for buyers and sellers) and provide video meetings through an integration between Zoom and Cinando. Participation in the online market will require a one-time 180€ accreditation fee (which also includes 1-year's access to Cinando). For more information on the virtual marketplace see the official market website.