But isn't the coordinated network upgrade problem already solved? In the Bitcoin XT (sp?) thing, the solution was to not switch over until over 50% of participa

But isn't the coordinated network upgrade problem already solved? In the Bitcoin XT (sp?) thing, the solution was to not switch over until over 50% of participants reported being in a version that supported 2MB blocks. Core has offered a solution, but only 6 months after another equivalent solution was made and basically deployed...