As of the date of this post the name "Microsoft Edge" has just been officially announced as the default browser for the new Windows 10.
It may be premature to ask but I would like to know if a new Selenium WebDriver is available for it and if not, if there is any telling how long we might expect to wait until we see one developed?
(A technical preview of Windows 10 has already been out so this doesn't seem like a foolish question to me.)
Yes, there is a WebDriver implementation for Microsoft Edge. Its initial availability was announced on 23 July 2015. Language bindings in the Selenium open source project have been updated to take advantage of this driver implementation, and those updates have been released in Selenium 2.47. Note that the Java language bindings were re-released as 2.47.1 to correct an initial issue. The initial implementation has limited functionality, but Microsoft is committed to bringing a fully functional driver implementation to fruition, so updates will be forthcoming.