I would be highly, highly skeptical of anything that D&D Beyond says is in the works. Why on earth would Roll20 work with them to integrate? Roll20 has their own compendium which they want you to buy the MM, VGtM, etc for. They'd never be on board with letting you spend your money elsewhere and then integrate it into Roll20. They'd get nothing out of that. Also, D&D Beyond is run by Curse, which is a notoriously greedy company that quickly abandons projects once the initial hype is gone. Don't spend your money there.