[Kunzite]

The strange thing about Pentax is - at this sales volume, camera development becomes unsustainable really.

Maybe, if there was a Pentax Corporation making only DSLR products.
But Ricoh Imaging has a more diversified product line, with the Theta and GR helping quite a bit.

However, it seems as if Pentax has - at least to some degree - outsourced their lens R&D to Tokina/Tamron.

Definitely not! And you should know better.
I'm tired of repeating: there are only 3 Tamron-made Pentax lenses. There is one Pentax-made lens with Tokina-designed optics (the old DA 12-24). The others are Pentax.
The D FA* 50mm f/1.4 - which is also offered as Tokina Opera? It's a Pentax design. The DA* 11-18mm f/2.8, their latest new design? It's Pentax.

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Of course, I don't know who licensed to whom in the past but historically there were several lenses shared with other companies.
- 10-17mm (Tokina)
- 18-270mm (Tamron)
- 12-24mm (Tokina)
- 50-135mm (Tokina)
- 16-50mm (Tokina)
- 100mm (Tokina)

So in a sense, Pentax is already transforming itself to a third-party lens manufacturer.

Shared, yes, but why on Earth would you assume they are the other maker's doing?
From your list, the 18-270 is a rebadged Tamron, and the 12-24 has Tokina-designed optics. The others are Pentax designs (yes, shared with Tokina - because, surprisingly to some, Tokina needed Pentax more than Pentax needed Tokina).