Rumorednow is right, there is no promise of being able to port OWOS to something anytime soon, so best would probably be getting a Pre3.
But as i wanted to get a new phone anyway, i got a Gnex in the hope of being able to port something new on it sometime in the future.
Webosports tweeted last Saturday that together with HP they were getting closer to a beta release of OWOS for Gnex / N7, so my hope is on that.
Maybe Ubuntu phone will be portable in a couple of weeks/months, as i understood they are planning to put a device out themselves somewhere in 2014, but the software earlier.
Anyway, if you want to stick to webOS for now, buy a Pre3, its a great phone!