Maybe one day the iPad Pro + stylus will do wonders for visual programming languages like VVVV (can't think of any others).
iPad Pro has a 13 inch screen; that’s the same size as my MacBook Pro’s display. With a good keyboard, such as the one Apple sells, I don’t see why it should be difficult to write code in an iPad.
13" is barely bigger than the 12" display on my Apple IIgs (late 1980's), or my first laptop (mid-1990's). That was a perfect size for a VT100 emulator (it's the same size as the original 1978 VT100!), but that's not how I write software any more.
The same size screen is actually relatively worse than 20 years ago, because these days all documentation is online, so it has to share my screen.