The series has gotten popular to the point of being a valuable property, I have to assume their budget is increasing to boot. When more money is involved, they're going to take far fewer risks. They're going to make the game more casual, less challanging, and requiring less skill to appeal to as wide an audience as possible.
They're going to make a game that most people who enjoyed Demon's and Dark won't like, but will buy anyway because that's what happens. It's also going to be purchased by a much larger group of gamers who've heard it's more accessible, or have just heard about period from their gamer friends who keep on touting how awesome it is.
It's going to kinda emulate what make the first two games so great, but it's going to miss. It'll have a tutorial level, it'll have a hint system, the combat will be boiled down to a much more streamlined level. Parry system will probably be either ditched or made so simple that timing doesn't REALLY matter. Health will regen, stats will be condensed to attack, defense, and maybe stamina. Your souls will no longer vanish if you die before you reach them, if you lose them at all upon death. There will be fewer secrets overall, or they will be plainly spelled out somewhere. Being able to be invaded will possibly be an option you can switch on and off. Bosses will still probably be dangerous, but much easier.
This is all my cynical opinion talking, based on my experience with so many other trilogies that have dissapointed me in the third game. I do hope I'm wrong, as I love the first two games. Thankfully, those two games are so deep, I'll continue to play and enjoy them for a good while longer anyway.