The mainline Sims games have an overarching plot of sorts with things that happen to some of the recurring settings, Townies, and families. It’s weird though, the games also apparently aren’t in chronological order. Some youtubers get deep into it.
Not to mention explicit plot in many of the spin off handheld games that are more “Sims flavored RPG” than actual Sims games.
There also are recurring brands for items, and jokes in item descriptions that further connect things.
So they could dig deep from the source material if they’re motivated, but I can’t imagine the target audience for Sims “lore” tie-ins/callbacks is that big.
I expect they might pull from the absurd events that can happen in Sims 1 and 2, like the clown that spontaneously invades your home if you’re too depressed, or the humanoid bear that can show up to go through your garbage bins (and I think can use the stuff outside in your yard like a normal townie).
No matter how they do it, I don’t have much faith it’ll be anything good. Most likely just an exec’s coke induced plan to try and capture some of that Barbie money/audience while promoting the series. The last main game came out a decade ago, and the base game went free to play in the last year or two. Probably one last attempt to drive DLC sales before they announce the next one.