Ok, so I want this. And I want to pre-order it so I can get the Ice Lounge thing. But I own the Steam version of the game, and there is no preorder available in that format. However, I have downloaded the game and all the expansions and stuff packs I own through Origin, so I could use the Create a World feature.
I just checked, and I can indeed launch from Origin and it loaded up my most current save which happens to be in the custom world I created. I got the "some word items missing and were replaced" error, but everything seemed be normal in my sim's house (just happened to be the house I built for the Olympic Starter content, so this place is pretty small and was built to be only vanilla).
So, my question is, can I pre-order from Origin, download when available, and then play through Steam and have the new content and Ice Lounge available? My gut feeling is yes, but I'd love to have some confirmation. I don't really want to buy this expansion twice if it doesn't work.