After updating the game the base game lots, on the menu in which you choose which lot you want to play or build on, are with the new and updated lots. But when actually within the new lots and playab...
Ideas
I can further add to this. In existing saves when you first load in you will still see the new versions of the lots from the map level if you hadn't previously edited the lot. However, if you've edited the lot (either bulldoze, replace or renovated) you will see your lot right away without having to load into it. As the OP has mentioned, if you load the lot and go back to the map view, you will then see the original lot and not the new version.
Also, if you've edited some of the revamped lots and not others, you will see the new version of the ones you've not edited at map menu (until you load it and then go back to map view) and whatever you have on the lot for the ones you've edited from map view.
I attach an example of the Willow Creek map where I had previously replaced the Goth's home (Ophelia Villa) and the Pancakes, but not the BFFs (not sure re the Spencer-Kim's). You can see that the BFFs looks like it's the new version and the other two don't.
So this is just a visual issue for existing saves for those lots (of the revamped lots) that you've never edited.
Best regards,
Jennifer