Let's get one thing straight: C3 isn't going to be a 'native' engine (whatever the hell that even means anymore).
Why? Because there's a reason that an annual subscription to Unity+Exporters costs nearly as much as leasing a new car: it take a mega-ton of work on the part of dozens of developers to maintain compatibility across all those platforms. Everyone here calling for native exporters: do you want to pay an annual subscription fee of ~$100-200 to maintain them? I'm sure some of you would be willing...and most wouldn't.
Let's get to mobile, chief bugaboo on these 'ol forums.
Mobile is supposed to be a nightmare...but is it? Or are you thinking of Android?
We all know Android export is a bit of a mess. Guess what? Android is a mess period.
It's a massively fragmented market with half a dozen different OS variations, a million different hardware variants (many of which are complete trash), slow adoption of updates, rampant piracy, and a metric sh!tload of shovelware dominating the charts. Oh, and with wireless data limits being what they are, everyone with > 3 brain cells runs adblock.
The success curve on android is weighted crazy high, with behemoths like Supercell sucking up most of the money that does flow into the platform. So...why is it even worth bothering, except to maybe license something or to add to your portfolio...or just publish for fun? And if it's the later, more power to you, but why not just develop for PC where you can make what you want and not have to worry about performance (unless you are making some terrible coding choices)?
I'm not completely defending Scirra here. Going back to the jank issue: The choice to update to a defective version of node-webkit -- and stick with it even though regressing to 10.5 was clearly the best choice in the short term -- was a massive mistake that shook the faith of less technical users by breaking games that weren't really broken. There is really no reason that should ever need to happen again.
Let's do with NW.JS what we do with C2 itself: have a stable/beta cycle, where beta is the newest version of NW.JS available, and stable is the newest version that works without issue. Let NW.JS break for months...as long as our stable branch sticks with a functional version, who cares?
Consoles are where things get tricky. It's a damn shame, but having console exporters just doesn't look likely, unless Sony/Microsoft decide to get behind them. XBOne and PS4 both have sufficient grunt to run C2 games, but there simply isn't a HTML5/WebGL engine of sufficient sophistication for either platform. XBOne there might be a chance (Microsoft is very gung-ho on 'run everywhere' all of a sudden), but PS4 is still top dog for now, and Sony has always been an odd and stubborn company that's more than willing to cut off their head to spite their left nostril (so to speak). If they don't want to do HTML5 they won't. Period.
Overall, I think Ashley is dead-on with C3: keep improving the engine we have now, make an editor that can be customized and continue to evolve with the engine, and make it easier to build games in a more modular way so we don't have to re-invent the wheel such much. Consoles are the one missing link that's a damn shame, but I don't think there's much we (or Scirra) can do about that.