Old news, about a month old. But it's good news for sure. Hard to say how many copies have been sold in this day and age where you can rent the game or where multiple family members can play it on the same Xbox with different Xbox Live account, but I would have to assume the number is over 6m sold. The current bestselling Forza game, Forza Motorsport 3, sold 5.5m physical according to VGC. VGC has Forza Horizon 3 at 3.72m physical, but console digital is huge now, was over 30% when FH3 released and is closing in on 50% now, plus we know that Forza Horizon 3 sold pretty well on Windows 10, so over 6m sales certainly seems to be a possibility, making FH3 the bestselling Forza game to date.