Perhaps people are worried about creeps abusing a children's entertainment fandom, as seen with My Little Pony.
To be honest, I'd say the only reason we don't see as much of that with LEGO as with My Little Pony is that the LEGO themes that are most popular with grown men have very few female characters with well-rounded personalities for adults to project their bizarre sexual fantasies onto.
"Rule 34" is very much a thing in fandoms for other kids' series like Pokémon or Avatar: The Last Airbender, and even the AFOL community has found plenty of unique ways to corrupt the hobby (like "Bonktron", a series of grotesque phallus-shaped space MOCs which I've more than once had the misfortune of seeing). People just aren't as quick to judge the whole fandom for its skeeviest members when they hear about grown men liking a beloved toy from their childhoods as when they hear about grown men liking a show aimed at girls.
I expect next year's Modular Building to go back to around a Brick Bank price point, same as how the next modular building after Town Hall went back down to around a Pet Shop price point. Both Assembly Square and Town Hall were meant to be deluxe sets celebrating an anniversary of the series as a whole, although Town Hall wasn't as heavily promoted as such. So I wouldn't expect the Assembly Square to represent a new status quo for the modular buildings, any more than Town Hall was.
Now, when it comes time for the Modular Buildings series' 15th or 20th anniversary, all bets are off. ;)
As far as subject matter is concerned, I don't have any particular expectations, as I've never put much stock in the idea that LEGO plants clues for what their next building will be, nor that they follow a strict pattern for the type of buildings they release. I'm not too particular in what I hope to see, either. Just something that feels fresh and new. Maybe a combination bowling alley/arcade, or a police station?
One thing I would like to see, especially now that LEGO has a wheelchair mold, is a modular building designed for accessibility — for instance, something with an elevator instead of stairs like the Town Hall, but also with a ramp outside instead of just a stairway.
According to the last six months' BrickLink sales, a new copy of #9446 Destiny's Bounty is currently worth around 75% more than its original sticker price from five years ago. That's not Star Wars levels of appreciation, but it's nothing to sneeze at for a theme that is outside many AFOL's radar.
Seeing as the new Destiny's Bounty still has cloth sails (a big draw for Pirates fans) in addition to a much more impressive build, I'd say go for it. And if you see a similar discount as it gets closer to EOL, pick up a second copy so you have one to build and keep for your own collection!
I don't see this as being really viable. You'd probably need each set to sell at least 10,000 units to even be worth producing, and that's assuming that it didn't need any discontinued molds to be reintroduced, which would raise the production costs even more and require producing even more units to adequately subsidize those costs. I don't know how many people would be willing to pre-pay for a re-release in the way you're describing. Also, LEGO has tried re-releasing classic sets with far fewer obstacles and strings attached in the form of the LEGO Legends line and it wasn't profitable. I don't believe that was a case of the sets being wildly overproduced or anything like that. The demand just wasn't there.
Even if all these obstacles could be overcome, I don't see any way that this would be a better use of the LEGO Group's resources than producing actual new sets that meet today's higher design standards.