It's tough to recommend exactly how any one person should upgrade their flute because there are so many factors involved. For one, no one flutist has the same flute journey, so an upgrade that might work for one flutist may not work for another. Everyone's budget at any given moment is also different. Each flutist may also not be exposed to the same brands of flutes as another might. There are too many variables in the experiences of a flutist for me to tell every last flutist what would work for them.
It's a journey we all need to experience and walk for ourselves.
I'm still in the midst of my own journey, and to be honest, I don't think this journey will ever really end. As long as I play the flute, I will need to keep saving up for the next big upgrade. Think of it like leveling up in a game, except in this game of playing the flute, leveling is uncapped. To use gaming terminology, we have to "grind" in real life to get better, and with each "level up" in our playing, we need to find equipment to match our playing.
Happy leveling! ;)