We've had 40 nm Bitcoin ASICs be more efficient than 28 nm ones, so stop with the process size obsession already.
But again, those are not Bitcoin ASICs, but just measly SHA-256 instructions, which isn't what the Bitcoin ASICs do. Please stop ignoring that simple fact.
Bitcoin ASICs do not simply SHA256(x), they do the whole "search for SHA256(SHA256(x+y)) and gimme y when the result has zeroes".
They're not "just measly SHA-256 instructions", they will be hardware. Yes, I understand that BTC ASICS are doing the exact equation and I'm sure the mobile chips won't be. But there is more to it than that - and I don't just mean process size (which is a huge deal, and the obsession of every chip maker out there, including the ASIC guys). Indeed, if you've heard of 40nm ASICs beating 28nm ones (really?), then you've already alluded to this.
A handful of bootstrapped ASIC makers has nowhere near the chip design expertise of the multi-billion-dollar mobile industry. Cellphone chips have every energy-saving optimization trick in the book. ASICs don't.
ASICs are getting more efficient, sure, but that's down to the process size and not much else. They're certainly not designed to be mobile. Even the USB ones only just scraped under 5W.
So yes, I do get your point: these things won't be true 'baby BTC ASICs', but they'll still be ridiculously energy-efficient and kicking out well over a GH/s per Watt.
And more to the point; there will be millions of them just sat there every night doing absolutely nothing but watch a battery charge - and some web-crawling. We'd be crazy not to tap them for mining as well.