Goodbye, not au revoir.
I've been doing web development for mobile now since 2000, when the company I was working for, the late and lamented xoo, got a contract to build a document-sharing site for a dotcom boom start-up (what are we in now? the dot-ly boom?). Tomorrow I leave all that behind for a company which is just web.
I have known and tolerated all flavours of WML (except WML 2.0 - no-one used WML 2.0), XHMTL Mobile Profile, Basic, 1.0, 1.1. I've seen the appearance of colour graphics greeted like a second coming. Most significantly, I've seen the iPhone shatter conceptions of what a mobile user-agent should do.
(In 2005 or so we used to argue about who's responsibility it was to make the real web render on devices: should mark-up be corrected in the network, paginated and sized properly; should correcting the mark-up be forced on the authors; or should the browser vendors build better browsers. Mobile Safari killed that argument stone dead. For the record I was of the view that browser vendors should stop dicking about with optimised rendering (Opera Small Screen Rendering, looking at you) and just support the existing standards. With no major bugs. Unbelievably rare on a mobile device c.2005)
In those 12 years mobile development has gone from being a specialist backwater requiring much nurturing and specialist knowledge to a mainstream activity, with its own narcissistic conference circuit and unshakeable dogma (truly the sign of maturity).
And that's why goodbye. From now on mobile is just part of web dev. There are differences, sure: you don't interact with a phone the same way you use a laptop. You don't want - always - to consume information the same way. There are always going to be technical differences between a touch surface which can't be bigger much than your hand (there's a reason we mentally classify tablets differently, and why Samsung's Galaxy tablophones cause such dissonance) and a big screen at arm's length. Personally, I don't think responsive web design is a sensible response to the problem; far better to do the hard work where the user isn't going to notice it.
But if you're not building for both, you're not doing your job properly. AR glasses, TVs, tablets in all sizes further complicate the picture for web developers. We'll look back on the period between 1992 and 2012 as being a naive time when you could afford to develop completely separate products for different devices.