I find it pretty unlikely that WP share will go up like on the above graph. No reason for it really, I'd say it has about peaked for now.

Reason: Up to now there's been just a trickle of WP devices other than Nokia Lumias; I mean, all I have ever seen are the single HTC & Samsung devices on display @ shops, I have never never ever seen anybody using one of those in real life.

Now when NMP --> MS, there will be no other manufacturers left who would ever again introduce a new WP device. No way, they just cannot compete with Microsoft, or would not want to.
So, Microsoft will be left as the only manufacturer of WP devices, there is not going to be a multivendor ecosystem ever.

I am willing to bet a lot the business is going to be a losing game for them. MS has got barrel-loads of cash to throw at marketing but in the end they cannot succeed in a free competitive environment. WP is just too, stiff, too difficult to succeed.