At the moment, here's how I think/hope they'll work based on what I've read.
They will require the Ritualist feat to access. If could be that Clerics and Wizards get the feat for free at 1st level, while other classes have to buy the capability from their allotment of feats.
Rituals will encompass 'utility' spells (teleport, etc.) from the old lists, spells with strange effects (Polymorph any Object, etc), Item creation, summoning/binding demons, creating undead or blowing up the world (maybe Armageddon, level 30 ritual).
Rituals will require money to cast, generally in the form of special ingrediants. Rituals may also have specific requirements to cast (eg specific alignment, hard to get 'quest' ingrediants like the blood of a silver dragon, etc.). Time will also be a major factor depending on the effect you desire.
Rituals will be divided up into lists depending on either power source or class as well as level. Hopefully power source. I also hope there will be general rituals available to anyone as well as martial rituals.
Rituals won't be granted to a PC for reaching a certain level: you'll have to find the formulae or a mentor who can impart their secrets to you.
Anyone will be able to take the Ritualist feat to gain access to Item Creation at the very least.
Now, I don't know if any of the above is true or not, or if things will change in the meantime, but this is where I hope they go with it.