The treehouse is indeed very well done. I'm still shocked WDI was able to radically alter the attraction without a direct IP tie-in (/merch opportunities). I've visited Disneyland twice since it opened and both times the treehouse was slammed. Let's hope it sustains its popularity and demonstrates to WDI/whomever that there is a craving for this type of attraction among DL guests.
And while we've heard some disconcerting rumors about the work being done to Mansion, I'll stand by my assessment that WDI has been pretty cautious with Disneyland upgrades in recent years. There's no reason to assume this refurb will be any different.
My expectations for Tiana are sky-high, but what I'm expecting is that it'll be a very strong modern Disney attraction, cut from the same cloth as Rise, (HKDL's) Frozen Ever After, Runaway Railway, Radiator Springs Racers, Na'vi River Journey, etc. In other words, it will be competent and fully-realized but maybe a little antiseptic. It will have AAs and they will be impressive but far fewer than the 1960s-1980s attractions. It will employ projections skillfully. The story won't include any real sense of danger, because modern WDI and the suits are afraid of scaring children. It definitely won't include anything challenging or artistic, because modern WDI and the suits are terrified of offending anyone. But it will be a pleasant ride experience with great music and friendly characters and endless opportunities for merch and food synergy. And it will add Black characters and (if what WDI is saying about the music and art is true) culture to Disneyland in a way that is joyous and celebratory and makes sense.
It will not resemble Splash in any way because WDI simply does not build attractions like that anymore. But in its own right, it could (and should) be a very strong attraction.
And at the end of the day, Splash (perhaps my favorite attraction of all time) was in terrible shape and WDI was never, ever, ever going to be able to acquire the funding necessary to adequately fix The Uncle Remus Ride. So best case scenario, our options were a modern-IP overlay or just letting Splash rot away forever. Neither option was ideal, but I've come to terms with TBA. And if we're really being honest, some sections of DL's Splash (such as the "How Do Ya Do?" section) were always pretty sparse and dark and kind of chintzy; at the risk of being accused of heresy, I think it's quite possible modern WDI might actually be able to improve upon some of those scenes by means of projections, modern lighting techniques, etc.