Your message is partially right. iPhones market share is heading down true but unit sales were still rising and have just taken a boost from China.
In the long term, your provocative heading may well turn out to be correct but that is years away. Businesses want their development done now on machines that are "out there" at present, not years away.
I would like it If Windows phones actually caught on but that one may be even further away. Their market share is so low that it could be hugely changed by a rounding error.
Businesses are shedding BlackBerrys at speed. There are two alternatives. Android for companies interested in cost, functionality and versatility or iPhones for appearance, coolness and keeping non-technical executives happy. Windows phones are somewhere in between but it is hard to tell as they are so rare.
I have just had my work BB replaced with an iPhone. Our department has provided support for them for years but now we are on them too. As I was aware, in comparison to good android phones it is limited and fiddly. Sending email is infuriating. I suppose the fashion conscious don't use email any more. I've got better things to do than look like a manager. I would have preferred a Note4. I could then leave the tablet behind. As it is, I read the email on the iShiny but if I need to reply, it's Android 7" tablet to the rescue!
Maybe iThings would fo the way of the Dodo if there was more than one alternative. At present, there is only Android and that is not favoured by the uninformable suit wearers.