According to various gaming sites, a recent Famitsu interview credits Square Enix's own Tetsuya Nomura as saying that the company plans to show new visuals of Kingdom Hearts III by year's end.
Of course, nothing specific was said reguarding what event might be privy to these exciting new "visuals" (presumably a new trailer). Tokyo Game Show seems most likely, being closer to the latter part of theyear.
Source:
PSU,
For the Reunion