I think it became the go to weapon in the 16th century, not the 15th. From my understanding the Swiss still used loads of Halberds and other 15th century weaponry regularly even after 1420-1430. They weren't all pikemen, nor was the pike the "Go to weapon" with most medieval armies. The Swiss still also employed plenty of other weapons including the Halberd as well. The Swiss just got really good and brutal with pikes before any others and used them to great efficiency against armies that weren't using them, similar to how the Macedonians were in Persia in the time of Alexander. as Macedon displayed - if you're on the right ground and terrain and have drilled well, really long spear walls with multiple spears jabbing at enemies that don't have weapons as long as yours is very efficient for rolling up the fronts and pushing enemies back. And that became the sort of go to famous weapon for the Swiss first.
I believe Halberds start going out of style more so at the end of the 15th century when Charles the Bold, who equipped a very professional army with state of the art gear and siege equipment, suffered so many defeats against the Swiss. Then in the 16th century when many more Landsknecht pop up pikes start to really get going all over. Halberds and great swords were also normally still seen in Pike blocks by the Swiss and Landsknecht because when they started doing Pike on Pike fights, the shorter arms up close like swords , halberds and the greatswords became very useful if you were able to get past the pikes and into the faces of the enemies. Allegedly they'd use these shorter arms to cut down enemy pike shafts as well and then use them to deliver killing blows when they got up closer.
It seems by the time you get to the 30 years war in the 17th century most soldiers have dropped halberds save a few officers carrying them to signify rank. By then you'd have more guns showing up and the pike would be a good detriment to cavalry so you can stave them off from attacking musketeers.
Otherwise, I would say most armies for the majority of the 15th century still seemed to use Halberds and other types of weapons, and its really when the Landsknechts and Swiss are fighting each other and in the Italian wars in the early 16th century where you start to see more and more reliance on the pike.