I never downloaded CAW in Sims 3 so I don't do my own worlds but I used the templates from Sims 2 and I've redone every World in Sims 2 and 3, especially in Sims 3 where I like to use buildings from other worlds in the one I'm playing. The inability to even edit the town the way I could in Sims 2 in 4 is a big turn off for me and one of the reasons I no longer play it. We will never have that ability I don't think in 4.
If there is a Sims 5 and open world, CAW, terrain tools, create-a-style and all the life stages and the rest of it come back...? Well, I don't trust Maxis "vision" enough for that to happen. I get the sense they all are happy with what they've given us in Sims 4 and despite all the feedback, they still have no sense of why some simmers don't like it nor do they care.
