The Witcher 3 Expansions Will Be Comparable in Size to The Witcher 2

Gamereactor was able to corner for CD Projekt RED's Konrad Tomaszkiewicz a 13-minute video Q&A about the success of The Witcher 3: Wild Hunt and their plans to release more patches and two expansion packs - Hearts of Stone and Blood and Wine - that, when combined, will be nearly as big or possibly even bigger than The Witcher 2: Assassins of Kings was in its entirety. They've transcribed this portion of the interview, so I'll quote from that:

"The expansion packs will be whole new storylines with all the elements you've got in the main story (like cutscenes, new characters, new items, new Gwent cards) and many, many more. They will be quite long. The first expansion will be around 10 hours and the second expansion will be around 20 hours... and I think it's possible that they will be bigger, because it's always like this (that when we plan some time or hours, it's twice or something like this), but I'm not promising anything right now. And even now, if you sum up this 10 to 20 hours and you compare it to The Witcher 2, it's almost the size of The Witcher 2. And it will be cool, it will be new stories, it will be very emotional stories and I think that people will be happy."