You hit the nail on the head. Mobile revenues will decline for...

You hit the nail on the head.

Mobile revenues will decline for everyone because for years the entire industry has been gouging customers with voice + SMS costs.

If you think about what you can do with mobile data, why exactly do calls and SMS cost as much as they did (and still do to some extent)?

You can buy 1GB of data for $10 and that will buy you thousands of minutes of calls if you didn't have to dial a phone number - i.e. use Viber, WhatsApp, Skype or the zillions of other OTT services. SMS also costs nothing OTT.

There is a small premium to be paid for the priority of the voice service (i.e. you want to be able to make a call even if everyone else is streaming video) but that is now fully baked into mobile plans. Everyone has moved to unlimited calls and unlimited SMS plans. From here there's only two levers left - increasing data, and decreasing price.

Telstra hurts the most because they've had the fattest margins of the mobile carriers (built off their deserved reputation as the fastest network with the widest coverage... until they blew up last week, oops). Which is why as Optus and Vodafone step up their investments Telstra is IMHO in deep trouble.

Telstra managed to grow share under Thodey's reign because prior to Allan Lew taking over at Optus, Optus was pretty much asleep at the wheel. And at the same time Vodafone was going through its Vodafail saga. It's not often (and will unlikely happen again) that both your competitors go limp at the same time, and for an extended period.

One of the most telling signs of just how aggressive mobile competition is right now is the number of deals being posted to sites like OzBargain.

Yes, not everyone is a bargain hunter. I mention it purely as a convenient forum for an insight into the current offers available from the carriers + MVNOs - do a search for Amaysim, Jeenee (both Optus MVNOs), and obviously Optus, Telstra, Vodafone and TPG and pay attention to the dates.