I would imagine Tizen and Meltemi will use the WAC api for HTML5 apps that want to use device capabilities. Carriers are pushing to have WAC implemented so they can have their own app stores with offerings that work on all the smartphones they offer.

With regards to the C/C++ v JavaScript debate, you might find this blog by Havoc Pennington interesting: Embeddable Languages.

Personally I'd like to avoid low level stuff like C unless there's a bottleneck to alleviate, scripting is just easier.

It's better for manufacturers to limit 3rd party developers to managed environments too, it stops their reputation being tarnished by a crashing app taking the OS down with it.