In an interview at E3 Kingdom Hearts III directer Tetsuya Nomura has said that there will be bigger worlds with less transitions and a dramatic decrease in the loading times.
Although not to the same level of current generation open world titles, he said that KH3 will be far larger than it predecessors and will not feature the fade to black loading screens.
He also confirmed that at present there is more worlds in planning than there was in Kingdom Hearts 2, however that does not mean that the amount of worlds in the final title will necessarily be larger, news will arrive down the line on such details.
Controls are reported to be similar to KH2 however the additional use of the touchpad may change things up a little though even the team themselves seemingly have not make up their mind how the touchpad is due to be utilised.
In exciting but not entirely unexpected news, Nomura confirmed that there is due consideration given to online play for KH3, but stated that the team are concentrating on the main content of the game before considering their many ideas regarding online play.
For those who missed it, see below for the E32015 trailer for Kingdom Hearts 3, as well as the E3 2013 reveal trailer so you can see how much has changed: