Indiana Jones 5's performance will help us determine the level of public interest in the franchise, especially among the demographics that Disney is aiming for at the parks. But of course, the production of the film already indicates that Disney's research has determined a high demand for the franchise. So the biggest question is the demographics... which presumably skew older for Indiana Jones than Disney's main target for the parks. But maybe the new film will excite younger audiences (which is surely one of Disney's goals for it).
That said, I actually think that one of the main benefits of an Indiana Jones area (even if only a "mini-land") would be the difference in aesthetic/tone compared to the rest of DHS. It would presumably take place in some kind of forest or jungle, so plants and trees would be a dominant aesthetic - something we don't see elsewhere at DHS (including SWGE, which seems to be closer to a desert-type setting).
Although a boat-based attraction would also contribute to the eclecticism of DHS's attraction lineup, if they wanted something "faster," IJA has shown incredible staying power as a top-tier attraction for over 20 years at Disneyland (although I prefer the DisneySea version, because the Disneyland version relies a little but too much on blacklights against 2-dimensional backdrops, but presumably a WDW version would be "modernized," so I'm not worried about those issues with the Disneyland version being copied). Adding a version of the Paris roller coaster / Raging Spirits (or a more kid-friendly, non-inverting version of the same) would make it a really solid mini-land.
...unlike Splash or Kali, the level of “splash” can’t be toned down in the winter.
I know Grizzly River Run at DCA has two "wetness" settings that they switch between depending on the temperature, but I've never heard the same about Kali (seems likely that it's possible for them to do, since they're both standard Intamin designs). Do we know for sure that they actually do this with Kali? And if so, do we know if it's dependent on the day's actual temperature, dependent on the time of day, or dependent on the season? I've always thought it was unfortunate that Kali gets a few people absolutely drenched; it would seem more fun with a lighter amount of water, like Splash or like GRR during the "low" setting.