That doesn't make much sense.
People are going into panick mode because Samsung's sales are dropping and then they put all their hope in the Note 4.
We all know that even without a 5.5" iPhone, it would have been lines around the corner and a non-trivial amount of Android users would have jumped on that 4.7" iPhone like white on rice. There are already enough Android users that are frustrated that most OEMs don't even thinking about launching a proper flagship at that screen size...
The differentiator between Android and iOS never was the screen size. There are enough iOS users out in the world that we should all know why they stay so loyal to Apple, and why Android users are much more likely to OEM hop (or hop to another platform) than Apple users are to leave that ecosystem.
I'm double fisting an M8 and a Note 3 right now and under the skin they're still practically interchangeable.
Google, their services, their business model, their priorities, and the speed at which they innovate/adjust on Android is the reason why I consider getting the iPhone 6 (4.7", coming from bigger phones mind you). Not the fact that they released a 5.5" phone (I'm not paying $920 or so, after taxes, for a phone and a 16GB Phone is out of the question).
Apple's users will buy whatever they put out, and they always drag enough people with them due to the value that exists WITHIN that ecosystem.
When Google can eliminate that disparity, you won't have to sit there wondering if "a bigger iPhone" is going to doom the Note 4. When Android developers start to generally care about design, performance, support, and utilizing platform affordances as much as iOS developers, etc... Then the grass will not look so green on that side of the bridge.
The Note 4 at this point isn't anything special in terms of screen size. 5.5" phones are aplenty - some way cheaper than the Note, and 0.2 inches on top of that is ignorable. You can get a better camera with OIS in other, cheaper phones with 5.5" or bigger screens. The reason why the Note has been able to best other "Phablets" is due to the Digitizer + S Pen, it's position as a productivity device, and it being a Samsung device; with Samsung's marketing muscle behind it.
Take away the S Pen and Digitizer, and the Note is nothing more than the Galaxy S5 "Plus" - complete with TouchWiz's bad rep and the hoards of posters who bash it on the internet.