Well, FirefoxOS already has an OEM, so that's only 3. Firefox OS evolves from Boot to Gecko, telecoms and OEMs pledge support | Geek Pick | Geek.com
The only question mark left, to me, would be Sailfish and there's a high probability they'll be producing their own phones at the beginning: Jolla Phones Will Soon Be Available In Finland, Preview Of Phone Running Sailfish | Muktware
Much of this is already old news, guys. Like, half a year in some cases. Google is your friend.
Ubuntu probably won't have any problems, either, given their openness and opportunity for an OEM to truly offer a desktop and smartphone experience in a single device (and unlike the "Webtop" Motorola offered that was entirely problematic to use). I would expect an OEM or two to come on board by Q3 '13. Furthermore, developing for Ubuntu means an opportunity to cover desktop and mobile in one single application...and with the heavy hitters in development beginning to move to Ubuntu/Linux (it helps that Steam is coming to that platform) you can bet it's going to put up a fight: Operator and OEM partners | Ubuntu for phones | Ubuntu
Ubuntu (and many other Linux distributions) is also the ultimate in open source. Bar none. Linux set the gold standard shaping the modern open source movement, so you just don't get much more open than an actual Linux distribution as your smartphone OS. You'll see Ubuntu for Smartphones loaded on anything and everything webOS can, and plenty more than that. In far less time.
webOS is the only one of these OSes with zero plans for retail presence and zero revealed strategy to get there at present. Nobody will take it seriously until it does, nor will developers flock to it.
Will some of these eventually die? Probably. It's a crowded field, sure, but one has to assume the chances for webOS are simply not looking very good right now given the well-capitalized options (other than Sailfish) that are coming into the marketplace to take on the big guns with widespread name recognition, long-term user familiarity, a compelling and unique angle, and strong rapport from those that have used other products of theirs.
webOS to the world looks like a nice attempt that had some good ideas "at the time" worthy of incorporating into other, more successful OSes. Why? It failed not only once to gain traction after the Pre/Pre+/Pixi/Pixi+ build quality issues, but also the failure of the Pre 2 on the market (i.e., it went nowhere; failed launch), and then the Pre 3/Veer/Touchpad fiasco not even a year later along with Palm and HP's corporate antics and burning of bridges at every possible corner.
Well, and currently near-zero commercial developer support outside of a half-dozen folks here on this forum. Nobody
(except the folks here) says, "I want to develop for webOS."
Ubuntu alone brings in decades
worth of applications of every variety right off the bat and a massive existing user and developer communities, while Firefox OS (with their "WebAPI") allows any website to potentially function as if it's an app on your cellphone. webOS can claim neither of these innovations; these are completely unique to the extent in which Ubuntu and Mozilla are employing them.
For all the people that talked up and drew parallels to Ubuntu when Open webOS was announced, it's ironic that the same OS they held up as a shining example of the sort of underground popularity they wanted for webOS may now completely bite them in the **** because Ubuntu wants to be at the forefront of popularity in the mobile landscape.
In short, webOS can't sit there spinning on its thumb with Open webOS being the exact same thing as legacy webOS only on an improved foundation, relying on the same tired cards and gestures that didn't exactly drive success the first through third times around while everyone else shows off new features that are getting people's serious attention. webOS has to seriously up its game to something much, much more than it is into a mobile OS that brings something brand new to the table again just like it did when it was announced at CES 2009.
The only problem here is Open webOS hasn't shown anything of the sort and, despite the fact that I root for them to get their **** together and publicly demonstrate that they are, I can't say I have much hope that they will. Again.