In the good old days when people used to have 2G phones, they were expensive but all people cared about is Voice & SMS.
The initial 3G phones were bulky/heavy with small battery life, not many apps and expensive. There was not much temptation to go and buy one of these, unless it was heavily subsidised by someone. Naturally it took a while before 3G adoption became common. In the meantime, people had to go out of their way to get a 3G phone.
With 4G, it was a different story. Once LTE was ready, the high end phones started adding 4G in their phones by default. What it meant was that if the operator enabled them to use 4G, these devices started using 4G rather than 3G. Other lower end devices soon followed suit. Nowadays, unless you are looking for a real cheap smartphone, your device will have basic LTE support, maybe not advanced featured like carrier aggregation.
The tweets below do not surprise me at all:
Another data point for Turkey #4.5G: There were 5 million new LTE subscriber additions on the first *day* of launch. (no 4G before)— Dimitris Mavrakis (@dmavrakis) May 10, 2016
With Huawei in Istanbul for a 4.5G event. Apparently there are 40 million 4G subscribers 1 month after LTE launch (by all 3 MNOs).— Dimitris Mavrakis (@dmavrakis) May 10, 2016
This is what I refer to as 4G or LTE by stealth.
Occasionally people show charts like these (just using this as a reference but not pin pointing anyone) to justify the 5G growth trajectory with 4G in mind. It will all depend on what 5G will mean, how the devices look like, what data models are on offer, what the device prices are like, etc.
I think its just too early to predict if there will be a 5G by stealth.