i'm just making a quick interjection in this discussion as the topic (NOKIA strategy) isn't exactly fitting in this thread...

like you posted before, Symbian is still HUGE
1'300'000'000 units
the N8 has sold about 4'000'000 units still counting
and even though that number is far from the iPotatos numbers, the numbers don't compare directly because there a many NOKIA devices but only (really) one iP device (4 right now, 3GS being the cheaper alternative which will disappear as soon as 5 comes out & 4 takes that spot)
even though the time where NOKIA was selling more Symbian devices then all the other manufacturers were selling phones together are gone, they still are the biggest company in terms of selling mobile phones.
ANDroid devices come from many different companies and not all supply a "original" version of the OS and thus can't readily be updated to newer versions. at least not without losing property features.

what am i saying?
NOKIA isn't the towering giant of the mobile phone market it once was anymore, but it is still a major player and i think the management wants to keep it that way.
even though wp7 is still a very young and immature product, m$ has the deep pockets to bear w/ it and evolve it into... well, the dominant OS of the mobile phone market. makes sense to want to be part of this, no?
i have posted before how NOKIA could actually be trying to make the WIntel platform the standard in the mobile phone market as it is in the PC market (reason why they fused Maemo w/ Moblin to make MeeGo), so that it wll be running on future mobile phone CPUs from Intel natively.

i don't remember the details but i think it was part of the agreement between m$ and NOKIA that the HW design would influence (to some extend) the OS; don't remember the details right now.