I think it might be an idea for the sims4, to hide the load screens. They could show something going on there still, giving us something to look at and on some occasions, something to even interact with during the load screen.

Some examples for the stuff that requires loading in sims3:

-going on vacation.
Would be nice if there was an airport, and we saw our sim(s) get on the plane. During the trip the view could be restricted to the airplane, a small area with your sims in it while the game loads the destination. The trip take a certain amount of time regardless of the load time being finished so that those with fast computers get to play here as well.
Sims could interact with each other, be scared of flying, seduce a stewardess, woohoo on the toilet,etc. Motives could possibly be frozen for the trip so the game has less to deal with while loading.

-Going to the city or another destination on land.
Sims could take a cab or their car for this, camera could be restricted to the car, showing your sims in the car. As they drive, the new location is loaded. Sims could talk as they drive, play car games, pick up a hitchhiker, etc.

-Loading wardrobe.
For this, the world could freeze and limit itself to the room your sim is changing in, focusing on your sim as they browse through the closet while loading. When everything is loaded, the screen to change clothes could pop up with your sim still standing in front of the closet.

This could actually work. From a technical standpoint, the interactivity would have to be limited, otherwise you'ld have a loading screen for the loading screen, but unless they can make it so you don't have enough time to read half a book while waiting for a world to load, this would be a nice idea.

Perhaps for car journets and plane journeys they could have terrible magazines for you/your sim to read. Updated monthly.

It's meant to be a small area yes. Hence just the car, just the plane and such. a small area for your sims to interact with as the area loads. In the car a very simple backdrop could be shown, only the car and the sims within being the only stuff seen. Camera view could even be fixed from a single angle if it would help cut down on memory use. Would just be a nice way to keep playing the game as it loads.

Though I would miss the "walk to lot" feature from BV. I guess that if a Sim wanted to walk, you can just have the sound effects .... a car horn beeping, a dog barking, a Sim saying the Simlish version of "Ow, @#$%!" if the dog bit it, a peppy tune ....

That would be nice, but I'd rather they did something to optimize the game so load screens are more like the 5-10 seconds of every other game. Something about the way EA packages data into .package files seems to be significantly slower than other games. Maybe it's a really inefficient compression, or the extra complication of using TGIs and GUIDs, I don't know. I do know it's extra needlessly complex. Gigs and gigs of data seem to load significantly faster from .bsa files on Bethesda games, which is a considerably simpler method of compressing/storing data files, for one example.

Maybe a good idea would be to integrate events, like a newspaper or town blog, where you could view births, deaths, marriages, graduations, festivities, and the like within the town. Didn't they have something like that in TS1?

Adding speical effects during the loading times will only increase the already long loading times, as it must load the loading screen data first, I prefer my imagination to run wild than just to see a sim get on a plane EA's way, so I would be fine with just simple loading screen(s).

I'd like loading screens with text instead of animations. Maybe some gameplay tips, cryptic messages and easter eggs.

I prefer the empty loading screen, because this feature will make you wait even more.

It could be like the new load screens coming to TS3: Into the future!.

Great idea. But I fear it might sacrifice some loading time because it would have to load whatever your doing and process your Sim's actions

Would it be that bad though since its gameplay, and thus part of the game experience?