This week, I discussed Instapaper founder Marco Arment's speculation about how a retina version of the iPad Mini might not be far off. Arment apparently can't resist taking the next logical step and prognosticating on the rumored iPhone Plus (or, um, Math), Apple's putative entry in the nascent "phablet" category. His illustration above shows the graceful, Fibonacci-like progression that would be Apple's mobile product line.