They are building KH3 up to be the greatest KH experience of all time. They're taking everything they built up in KH 2 and making it better. The controls will be solid, the techniques will be more awesome, and the story will be wrapped up perfectly, save for the post credit scene that gives us insight into KH 4 or whatever the next title may be.
EDIT: Okay, so since everyone else is going more in depth with their answers, I'm going to tell my story.
I was 11 when KH 1 first came out, I didn't have a PS2 yet because it hadn't become my birthday or Christmas yet. My brother'd gf came over and she brought her PS2 over and she had KH 1. I watched her play it a bit and I was hooked. At that point it was all I talked about, I had a PS1 and mostly played RPGs and Final Fantasy was all over that. Come my birthday, my parents took me to Gamestop and I got a used PS2, one memory card, and a copy of FF X and KH 1. It was a very magical moment for me. Fast forward 2 years, Christmas I found out by shopping at Gamestop with my mom that not only was my favorite series, Jak and Daxter, getting its third installment but there was a surprise (i didn't see any ads for it in game magazines until after it came out) sequel to KH! At this point we knew our parents bought us our gifts, so I got to leave the mall that day with my Christmas gifts, Jak 3 and KH CoM. Move forward a few months and I check every single gaming magazine I can and frequent Gamefaqs to find information on new games and there's news about an upcoming Kingdom Hearts game. I remember printing out the picture of the first look we got of Sora's new outfit and I was driving all my friends crazy talking about KH 2. The day it came out the release date was still up in the air because it kept getting pushed back but I remember I was hanging out at a friend's house and I got a text from another friend that it was out already and that gamestop was giving copies out early (I think it was coming out that or next friday) and I had my parents call ahead to verify they had it. As soon as they said yes to me my friend and i went straight to gamestop to pick up my copy and back and played it all night long. Unfortunately, like many others, I didn't like Roxas at first and decided I would skip 358/2 days (and thought it was a "side story") and didn't learn more about a new KH until BBS was announced at E3. That was when I was in college and met my wife and we bought her a PSP and BBS as a post Christmas gift. I skipped RE:Coded at that point because it was a cell phone game and everyone questioned if it was canon or not until I bought a 3DS specifically for Dream Drop Distance, I worked as a packer at amazon and picked it up on my way to work that day. A few months later, my first child was born. When I first saw that Re:Coded was Re:capped in DDD I bought it and regretted skipping a gem of a game. At that point I became crazy about theorizing where the story would go, making a formula for worlds based on what we already knew and watched every square enix event and announcement until that fateful day in 2013. It's long winded, I know but each and every Kingdom Hearts game has a significant place in my point during those times in my life and we got new info when my son, Axel Lea (yes that's his name) was born and we got new info again this year when my second daughter was born so every Kingdom Hearts release from 3 to 50 in the farthest future I reach will always feel special to me.