Firstly, the chaining method is still present in X and Y.
Secondly, it's mostly the same: there are some patches that will wiggle their grassy grassiness - the more they wiggle, the rarer the Pokemon will be in that patch of grass. The most major change is the term 'decoy patches' - something to make chaining a lot harder. Sometimes, when a grass patch wiggles, you can go to it, but sometimes a Pokemon won't appear, which will abruptly break the chain. :(
Your term of 'special Pokemon' is awfully ambiguous. If you mean legendary Pokemon, no, they cannot be found. If you mean Pokemon that can only be found with the Poke Radar, this isn't really confirmed yet, however there probably is, somewhere... xD
Hope I helped. :)