Exactly, they have such a short supply with the chips that they’re using them primarily for the compute modules (eg. the heavily embedded version that the “factory” Norns has), and only after that for the normal Pi 3B+ now.
So it’s more a short / medium term availability thing than getting discontinued… It sounds they might manufacture some 3B+ as well, or maybe not, but don’t expect to do so in large quantities this year so availability may be either bad or non-existent.