Anyone know yet if the PU protocol supports daisy chaining?  I might ask JopieK if there are any breadcrumbs about that yet. 

My assumption was that the Technic PU BB will be identical to the Train AAA battery box, except larger, with pinholes and AA batteries. 

I kind of assumed that there would be no PU receiver separate from BB.  

Now Ivan_M has me wondering if there will be a separate receiver, and if so, whether it would daisy-chain, which would reduce (doesn't eliminate) the stacking problem. 

2 outputs on the receiver, with daisy chaining, would mean the number of motors = number of receivers - 1.  I kind of doubt it though.

For clarity, I haven't drunk the koolaid about PU yet: the stacking problem is a problem.  I'm just waiting to see what we get in Technic before declaring doom.   For Trains, PU is a net gain over PF.  For Technic we don't know...so guessing games 

I don't think a separate receiver makes sense. Though to facilitate one motor powering multiple functions, I could see them adding switches/buttons on the HUB so you don't need to connect a phone/controller for that usecase.

JopieK's teardown actually mentions the main chip for the train BB is the same as in boost. So chances are they're going to use that for technic too, but at the same time since it's in boost it must support 4 channels.

With the reduction of complexity in the train controller, the price must have gone down, so I don’t expect any switches on the Technic BB/hub except on and off and every one will come with a cheap controller.  So Technic generic BB/hub will be the same guts as train PU hub with AA batteries and a controller... this makes every Technic PU model tablet/smartphone compatible... something I could see them wanting as a standard from now on. We will get a Boost type Technic hub with built in motors and two external ports, maybe a AAA version of the train PU hub with pinhole mounts, but more likely just the same box and using studded Technic beam connections to mount it. My thoughts are, think cheap, then think cheaper... none of what I have seen so far suggests anything else.

We Do 2.0 BB is similar to what you describe Bublehead, and I would guess we get a Technic SKU similar to that  https://www.brickowl.com/catalog/lego-white-wedo-2-0-bluetooth-wireless-smarthub-19071

The Boost form factor alternative: I don't want to be a broken record, but the Boost form factor would also suck for changing batteries. 

All the Boost models have to be designed to facilitate battery changing, including undoing the screw. 

Technic PF has a long track record of removable battery boxes.  That's just not possible when the BB also has integrated motors, they would have to be disassembled from the mechanism.

So a Boost-type Technic hub just makes no sense, it would be a silly SKU to produce: higher cost, more QA failures, less flexibility, negligible inventory benefit.  It makes sense in Boost, or for brick-built System RC models, but not in Technic.  I just don't see it.  Time will tell eh? 

@andythenorth, you make good points. I really hope TLG doesn’t  pooch this.