The thing is that fixing security bugs in old Androids just isn't that hard. I'm not talking about making Samsung upgrade their Galaxy S3 (a five year old phone) to Nougat (which also isn't that hard, Cyanogenmod (before it was LineageOS) did it, and the hardest part (back porting kernel features) is done by a very small team IIRC), but fixing bugs shouldn't be so much work.
The issue is that there is almost zero benefit for Samsung to bother.
So how will Fuchsia help?
Maybe now Google will contractually obligate companies using Play services to upgrade for X years?
How long will X be?
Based on Google's own history, I doubt it's going to be longer than 2 years since "flagship release".
Now this made sense when you got free phones every two years, so must people just upgraded then (why not?) But now that you actually lay out $800 on a flagship phone, people are holding on too their phones for much longer (and there's not much of a reason to upgrade, unless you're playing heavy games, SGS3 is perfect).
But we may actually lose something: If Samsung/Qualcomm can close source their kernel, it's going to be tough to build your own "Fuchsia." So even if you're an expert and shop smartly, you'll still be at the mercy of your phone manufacturer (see Motorola and their promise).
I read a linked article on here recentlyish that made an interesting note about the impact of Google being an advertising company: Android is Google's effort to create a defense moat by blasting a 100-mile crater around their ad properties. They can't turn Android into Broadway or a popup factory, but they can carefully court the DoJ (who fired the antitrust case at Microsoft in the 90s) and creatively push the boundaries.
Looking at it that way, Google have little incentive to rock their own boat.
There's also some interesting ponderation to be had considering why Android BSP propagation/vendor branding works the way it does in light of the above. Absolute device control (aka a flagship device) is likely only an option for Google (and Microsoft, thinking about it!) because of the competition; in fact now I wonder how fine the line is that Apple's skating (although I imagine the competition is what keeps them going as well).
In any case, I see Fuchsia as Google's equivalent of Microsoft Singularity. I'm trying to figure out what kind of point they're making by developing it in the open; they've likely gone through a hundred similar initiatives internally, as did/have Microsoft. Although now I think about it, Google do seem to have some practical business/real-world targets to hit with this (IoT is the likeliest actual hit) so maybe they're just publicizing it for that reason.
Regarding the openness of the kernel, all I can do is hope like mad that the kernel generally stays open on production devices (in "end-user" mode), or that there's some sort of developer option (and hardware, if necessary) available. And I can only hope like mad that Google figured out and appreciate the massive value of an open device, and don't do anything monumentally stupid. Fuchsia has an open repository, at least, which is a very nice start.
The thing is that fixing security bugs in old Androids just isn't that hard. I'm not talking about making Samsung upgrade their Galaxy S3 (a five year old phone) to Nougat (which also isn't that hard, Cyanogenmod (before it was LineageOS) did it, and the hardest part (back porting kernel features) is done by a very small team IIRC), but fixing bugs shouldn't be so much work.
The issue is that there is almost zero benefit for Samsung to bother.
So how will Fuchsia help?
Maybe now Google will contractually obligate companies using Play services to upgrade for X years?
How long will X be?
Based on Google's own history, I doubt it's going to be longer than 2 years since "flagship release".
Now this made sense when you got free phones every two years, so must people just upgraded then (why not?) But now that you actually lay out $800 on a flagship phone, people are holding on too their phones for much longer (and there's not much of a reason to upgrade, unless you're playing heavy games, SGS3 is perfect).
But we may actually lose something: If Samsung/Qualcomm can close source their kernel, it's going to be tough to build your own "Fuchsia." So even if you're an expert and shop smartly, you'll still be at the mercy of your phone manufacturer (see Motorola and their promise).