Canonical's speculative sales numbers may be further deducted by their Edge crowdfunding campaign that resulted 37K people participating forming only 40% (~13M $) of their target.
For people who don't know, these numbers are very, very small. I wrote an app store dice puzzle game on Android no one here has heard of and it has 20x those numbers.
As a developer, you have to decide if the decreased competition on the platform is worth the smaller user base when you decide if you will write a version for that platform. So platform size numbers like these are important.