Speaking of merely Europe, I'd expect anything could happen including what you say. But lets just not forget that the playstation/sony brand in Europe is far stronger than Xbox, which does affect the competition.
My humble opinion is if ps3 can be priced below $400 in a year, it will surpass Xbox360 but I dont think this will ever happen cos of the huge extra costs to sony.
Playstation 5 vs XBox Series Market Share Estimates
Regional Analysis (only MS and Sony Consoles)
Europe => XB1 : 23-24 % vs PS4 : 76-77%
N. America => XB1 : 49-52% vs PS4 : 48-51%
Global => XB1 : 32-34% vs PS4 : 66-68%