No-one will know until at least a few days before release when reviewers and testers get their copies.
There are region lock codes used with DS and 3DS games, at least one of which denotes a region-free title (though I am yet to see a 3DS game with the region free code). I will not be listing them all, just those which are relevant.
Take Super Pokemon Rumble (Pokemon Rumble Blast for those in the USA as an example):
It's code is: LNA-CTR-ACCP-AUS
for the Australian version.
The structure basically follows like so: LNA-CTR-abcR-CNT
Note: Not all titles may begin with LNA-CTR but that's what I have seen so far.
The section 'abc' denotes the Game ID, that is unimportant. The section 'R' denotes the Region Code:
J - Japan E - Americas P - Europe/Australia K - Korea O - Other/Undefined (in other words Region-Free, observed only with DS titles so far)
The section 'CNT' denotes the country of distribution: JPN - Japan USA - Americas EUR - Europe AUS - Australia KOR - Korea
Note: For DS games, this information was only relevant for DSi enhanced titles such as Pokemon Black/White/Black 2/White 2, as all other DS titles were effectively region free. But since all 3DS games are locked, this information is even more relevant. --- We shall rise again to start anew. White FC: 0862-2660-4156 / 3DS FC: 2492-4470-1418 / White 2 FC: 4556-7836-2644