Mountain bike tire/wheel sizes

In what seems to be perennial efforts to churn the market, mountain bike
designers went from 26" (ISO 559) to the ones knicknamed 29" (ISO 622,
same as 700C) because they claimed the 26" was too small. Then they soon
claimed the 29s were too big, so they started selling what they called
27.5" (584, same as 650B), supposedly "just right."

Does anyone know how successful the latter size has become? Is it a
dominant size now? Does it look like it's going to stick around, or is
this likely to become an orphan - as in "nobody uses that any more"?

--
- Frank Krygowski