Those BGA APUs are for the embedded segment, AM1 APUs are for the consumer market.
That is because there is NO chipset in the motherboard, the Kabini and ATOMs are SoCs, the motherboard only has the I/O connections, that is the reason they are cheap.
Its not about the TDP, it is the specifically segment Intel and AMD are targeting with those Kabinis and ATOMs. They targeting a different market than Haswell/Trinity/Richland. They may be some of the High-End products from the Kabini/ATOM SKUs that overlap the cheapest Trinity/Richland/Haswell SKUs but that doesnt mean they targeting the same segment.
35W TDPs Haswell Celerons are in the same segment.
I understand all of that, nevertheless, no one cares for what are they intended, we decide what to use in each sector, what i gona do first, as well as everyone, is to look at prices to consider the avalible options, them the pro and cons of every one of them according to needs.
If im making a desktop matx pc, who cares if its pasive or not? who cares about 20W? Price/Performance its the winner here.
If im making a mITX pc thats still holds true, while the prices might go a little in favor of AM1, its not enoght.
If i need to make a pc as cheapest as possible, ill probably go with a Sempron 3850, that still feels like the people buying C-50s, its an option, but not really a good idea.
If i need to make a HTPC i gona go for either:
A) a BT-D, why? because BT-D is passive, thats is a big thing, and its enoght for multimedia usage.
B) 7850K, why? to enable basic gaming
C) Haswell+dgpu, G1820+750TI is a great option for this, 750K as a option.
D) Core I3, software playback.
E) Celeron/Pentium/I3 passive
What even the point of going for a Kabini here? even considering that it uses less power than BT-D(and its hard to belive and still may not enoght to be worthwhile), ill need to spend extra money in making it passive, for what? BT-D can do the exact same thing for less money, you are not gona tell me someone really plans to do gaming in those things on a +32" TV running at resolutions of 720p or less.
Also, the G1820 can do it even better for same money and a bit of extra Ws.
Im not saying no one gona use it, there is always someone that will need something very specific.
About the upgradeability of AM1, no matter what AMD releases, the main problems gona still be there, Single Channel crippling the IGP, PCI-E limited to x4 2.0 max crippling dGPU performance, only 2 satas provided by SoC, active cooling, cheap MB and expensive CPU.... ill say there is not even a point in a socket, especially about that last thing.
I do see a great potentials of Semprons/AM1 sales, but no much else.