Blizzard has vowed not to replace Diablo 2 with Diablo 2: Resurrected.
In a video Q&A below, principal designer Rob Gallerani said "no, absolutely not" in response to the question: "will D2:R overwrite an original D2 installation?"
"Everything you have about D2 currently will stay D2. This is a separate product, separate game. You can play 'em both at the same time if you want."