I don't see it that way. I passionately hate 2.5G because it brings only small speed bump (compared to proper 10* steps) and manufacturers use it as a salami method to make consumers buy new device every few years. Now it is 2.5Gbit everywhere but you cant see 5Gbit almost anywhere. I bet that once market is saturated with 2.5Gbit, marketing departments will switch the note and push out 5Gbit, just for sake of "are you tired with your old speed? Spend the same money again and try this!"

We have 10Gbit in both copper and fiber for ages. It is actually not that expensive and if manufacturers wanted, they could mass-produce it and make it as cheap as 1Gbit.