I saw someone say Sakurai didn’t actually say “a while” in Japanese, but I don’t speak the language so not sure if that’s true or not…
I am merely an intermediate learner of the language - and thus far from a native speaker - so please do apply salt to this post:
After listening to his words during the "a while" portion of the video a good amount of times, and doing my best to put what I'm pretty sure I'm hearing into writing (plus looking up the words I didn't recognise), I cannot identify any Japanese word or phrase that is equivalent to "a while". I believe what he says is as follows, more or less: "We'll see you next time until we announce [the next character], but as promised, we will release it by the end of this year, so please wait." Or, in Japanese: "hirō suru made ojikai itadakimasu ga, yakusoku doori, kotoshijū ni wa hatsubai shimasu no de, omachi kudasai." (「披露するまでお次回いただきますが、やくそく通り、今年中には発売しますので、お待ちください」)
However, him saying this is quickly accompanied by subtitles in the Japanese version saying "披露の時まで、もう少しお待ちください" - "hirō suru no toki made, mō sukoshi omachi kudasai", meaning "Until the time of announcement, please wait
a bit more." So, in conclusion, Sakurai did indeed never say "a while" in Japanese himself, but subtitles in the Japanese version of the Presents did communicate a similar message. Maybe it was something he realised he wanted to add post-recording, so he told the Japanese editors to do so, and the English translators followed suit, if they weren't explicitly told to make that point clear as well. Or maybe it wasn't on Sakurai's urging. We may never know the exact motivations, if there is more to it at all.