I doubt they can do anything about the world sizes or make them livable or water swimmable, or I think we'd seen it by now. I've read somewhere on the forum that they said it would break saves. It might just be a rumor but it does sound reasonable.
Now if I was in charge these are things I'd add:
Dine Out: In addition to everything already said, a counter top host and waiter station, and the ability for those to work on other lots. I would also add the ability to live and run a restaurant from the same lot.
Outdoor Retreat: Given my belief that you cannot make the water swimmable, I'd make more tools to allow us to make pools look more like lakes. A pool border that looks like grass, sand, dirt or rocks. A jumping tower that looks like ordinary stones, where sims can climb up and jump from. Plants that snaps to a pool's edges. I would also add a tent that needs to be assembled where the assembly is a group activity that is affected by skills (handiness), trait and combability of the people doing it. The assembly could work or not, and be poor, normal, excellent or outstanding (the first would fall if it storms and be wet if it rains). A climbable tree for kids (where parents could be fearful and discipline them or proud and encourage them for climbing.
My Wedding Stories: Fix the bugs with the wedding ceremony!! Square buffet table with more options for food and possibility to have a different spread for desserts or breakfast.
Laundry day: under the counter machines, more swatches for the tub including more wooden ones, a really old looking washing machine (30s-40s)
Horse Ranch: Rocking horses for toddlers and kids
Get to Work: A browsing option on all hanging clothes in game and more hanging clothes in game, a changing booth (buy clothes, try on clothes, nap, cry it out, woohoo), more slots on shelves, more things to sell (produce, flowers (individual such), nectar (not only the one you make, a sellable version just for stores)... The option to run a retail store from your home.
Seasons: More holiday icons, more holiday activities. Some seasonal events in various worlds (Winterfest market, Egg hunting events in parks, Time love festival to love day when you have both seasons and city living, Fleemarket only in spring and summer if you have both packs.
Parenthood: I would settle for rebellious being rebellious, kids not waking up in the middle of the night because they suddenly found out they're picky eaters, and kids stopping making messes when they're disciplined (rather than parents waiting until they're done before they tell them off). More argument options would also be good (Argue about significant other; Argue about friends), and nagging options (nag about having children/wanting to be a grandparent)
Snowy Escape: A sledding slope that can be placed in other worlds so you can go sledding with your kids in the local park. Teahouse venue (with a working tea set and tea ceremony). Japanese holiday events, holiday icons and holiday objects.
Spooky: Table top carving station
Perfect patio: More hot tops, a submerged one (in the ground) and a tiled one that was made to be placed in pools.
Get together: A more old fashioned espresso machine, toddlers, infants and animals as club members, new filters (university student, foxbury student, britechester student, male, female, the individual branches of the various careers, livinglocation, more income brackets (§100 000; §1 000 000). More activities from other packs as well as "work related activities" for clubs that work as work places. The option to edit clubs from the main world page, the ability to decide on my own if I want 1,2 or 10 clubs, the ability to autogenerate members (per club basis). The addition of all types of venues as possible club gatherings.
Unfortunately I think the complete refreshes are gone. They ran a test with Spa-day, and figured it didn't pay enough. The sales probably didn't match the costs, or at least not to the extent they wanted it to. An alternative would be to add free SDX drops with small things for the packs as well as base game. Like one or two minor things that is for a pack (a changing booth for get to work one month, and a sledding slope another).