Hopefully, the burning will be conducted carefully -- as Laurel Neme, an expert in wildlife forensics, points out in National Geographic, ivory burning is not always successful, and the ivory can wind up back on the black market if it doesn't burn entirely:
Unless the fire is sustained at high temperatures for long periods of time, burning does not destroy elephant ivory. Instead, it chars the exterior and leaves the inside intact.
The U.S. Fish and Wildlife Service (FWS) National Wildlife Forensics Lab confirmed the difficulties of burning elephant ivory during experiments it conducted under controlled conditions at a specialized arson facility in 2008. Using oxygen-enriched propane to generate ultra-high temperatures (roughly 1,800 degrees Fahrenheit), an ivory tusk lost about a quarter ounce of its weight per minute. At that rate, depending on the temperature and duration of the fire, and the size of the ivory pieces, it could take months to burn one ton of ivory.
This explains why many countries choose to crush ivory rather than burn it -- the U.S. did so with 5.4 tons in November, and the Philippines did the same with five tons back in June.