I own an Xpulse 200 2V (purchased in 2021), and have ridden about 53,000 km on it. Recently, I test rode the 400X and X440, and I'm also thinking about the KTM ADV 250 because I want more power now. I’m 6 ft tall, so the X440 feels low. I’m undecided between the 400X, KTM ADV 250, or possibly another bike. I was waiting for the Xpulse 421, but I don’t know when it will launch.

Since you have mentioned you want a powerful motorcycle, we would recommend you look at the Triumph Scrambler 400X, KTM 250 Adventure and TVS Apache RTX 300 in the ADV / Scrambler category. Of the three, the Triumph bike is the most powerful, but it is also pleasantly usable inside the city, whereas the KTM and TVS are more do-it-all machines that will also be wonderful on a day-to-day basis. 

Coming to the Xpulse 421, there's no official communication from Hero on when it will be launched, so we would recommend going with any of the other options you are considering. 

Take a test ride of whichever option you shortlist before you choose.