Well, as was already reported here, CTO Mosconi said in a recent interview to Jolla Italia, talking about TOH that "In fact it will allow hardware upgrade without a need to purchase a new device." Considering that Jolla has been quite vague about most of the specs, that's quite a bold statement, so I don't think TOH will be only good to make funky covers, but agree with what you say that they will just provide the capability and wait for 3rd parties to develop something with it.
I want that confirmed from jolla! Not from some halfbaked google translation! Because there are other stuff that also he said that people here now has mistraslated or has not read correct.