I think that if Sims 5 is to be really impressive, it needs to be really flexible. The player will need to be able to choose the set up and the game will need to cater to the different major playstyles.
I think what we saw with the creation of the story mode sims is more in line with how it might go. By that, I mean, when the player loads a new game, they tell the game how they will play it whether that's focusing on one sim, one family or a rotation. There would be the option to have story progression or a completely blank world with no story progression where the player fills it or the game generates townies (possibly based on the player's specifications). The player could then later shift the style of the game progression in the settings.
If it caters too heavily to one play style, it will end up back in the same position as the other versions.
I enjoy how my own game is going. I'm exploring some of the packs further and things are getting more interesting for me. I have no need to move onto a new game any time soon, but I'll look at how things actually play out.
I know the old pattern but if they kill TS4 shortly after university, I'll be disappointed. I'm definitely not ready to start over again right now and I want to see new content. If that new content is in an entirely new game that starts all over, I'm just not there now. Whether I'll get there? I don't know. I'll make that decision based on how things are handled. As it is, I've set up an entertaining game and I'm playing that for the time being.