I've read a bit about the new rav. Looks like it's a step toward being more direct competitor with the Jeep Cherokee. I suspect the Highlander will also get a version of the same parts to be more directly aligned with the Jeep GC. Or at least have a model that is pretty similar in market.
What I've read suggests it may have some pretty neat features. Namely *real* torque vectoring with ability to overspeed any individual tire. If that's actually true (I'm skeptical) it means it has a planetary gear set on each axle - or maybe a planetary in each side of the center diff to overspeed that axle then brake one side? I have no idea.
My best bet is that it's simply the same awd transaxle they've used for a decade, only balanced ring gear front/rear (currently front diff is 4.40 rear is 2.20 so the torque split is heavily front weighted). Current version in the Lexus models does have a push button center diff lock. My guess is that it's the same thing in the new rav4 with brake based traction control and a matched gear rear differential. If that's the case - it'll be very similar to the Jeep products in how they go about doing it. And it would probably give an SR5 a run for its money in stock form - not durability, but capability on a trail on a given day. The SR5 will probably do the same trail every day for 20 years that would destroy the Rav in a few weeks. BUT... lots of folks like the Jeep GC and it's the same idea. Works pretty well for infrequent trail duty.
I think the Lexus IS/GS awd platform is ripe for transfer to a Highlander. It's a separated front differential and a much more complex AWD system that RWD biased and can transfer 100% of torque anywhere. If that is the basis for the new RAV - I'd be shocked, and also really impressed. It's the best AWD system I've ever owned. Much better than my RX350, and kinda wasted on a sedan IMO. It belongs on a crossover that's dipping a toe in the offroad world. It has a real transfer case, front drive shaft, and a front diff that's very similar to a 4runner. It's practically built for this - if they'd ever do it. Highly underrated because it's not put in the right platform. It requires longitudinal engine mounting among other things and packaging for a grocery getter isn't easy.
It will not be a viable replacement for a 4runner though. For starters it's a transaxle. That means no lifts other than very mild because you can't drop the front differential and the entire structure makes it very hard to do much with. Like a Honda Ridgeline. It's just not made to be lifted or be possible to lift much or at all.
And Toyota has said recently that it intends to keep the 4runner and add another smaller SUV that is body on frame and has long travel suspension to compete with the Wrangler. They said that the 4runner and Highlander are nearly identical on paper - but have completely different audience. They recognize that the Rav4 is the same way and a same size body on frame true offroad vehicle is both viable and in the works for the USA market. I'm curious to see what happens in the end.