If I had to guess 6e has D&D shift to be more live service. 4e failed at this, 5e is having increasing success with D&D Beyond. 6e will have them pushing hard in that direction again as the potential profitability is too promising to the suits. I expect the lesson learned of tailoring the game to the players will be lost and instead the game will be tailored toward monetization. They would love to have an AI DM service they could charge for. There will be more player option bloat as they chase the whales. They will probably be more restrictive of digitally sharing player option content. Only available if you purchase it or DM plays a steep fee for sharing.
In terms of gameplay, i think they'll adopt more digital friendly rules for things like stealth. I actually expect class strcutre to say similar, though abilities and balance may change a bit. They will have to do something about low level control spell proliferation. Possibly nerf those spells, possibly buff martials.
That's my expectations.