We have been seeing leaks regarding this new button on other platforms as well, and it is widely speculated that this new button will also be a solid state one, but there is no concrete evidence yet. Personally, it does sound a bit odd that Apple is planning to add another button, given that the action button can be mapped to perform a host of tasks. But, it is what it is at the moment, and we will have to wait for a few months to see some concrete evidence for the same.
