According to Vivi, they need to make changes to the engine to create a good experience on an Arctic map, which is understandable since half of the Arctic map would be aquatic, with swimming mammals. So far, we don't have any swimming mammals; the Beaver will be the first, and I assume it will serve as a basis for designing the others in the future. The other problem is the enormous amount of water and floating ice that the engine will have to render, something that has never been done before, so we don't know if it's even possible.
We have already received official confirmation that there are engine problems creating Africa 2.0 with elephants and giraffes, due to their size and that no lodges is prepared to place them taxidermied.
We just have to hope that they can fix it or if it is possible or they have the time to do so.