I’m not sure it’s that unrealistic. The trailer shows off a LOT of features carrying over from CS1. Some stuff might be cut, sure, but they aren’t swapping engines so the breaking changes might not be as significant as one might expect.
It wouldn't even really make sense, for example the Snowfall DLC only had permanently snowy maps, no snow was added to existing maps or maps from other DLC. CS2 will have dynamic seasons and climate. So asking for the Snowfall DLC in CS2 is asking for a feature regression.