Unlikely. Apple doesn't want you to be able to upgrade or replace parts on your Mac, they want you to buy the new model in a year.
I'd want higher resolutions as well, but of a standard resolution, not the oddball crap they used on the rMBP 15". Go with 2560x1440/1600 instead. rMBP 13" got this right . . . but the HD4000 IGP isn't powerful enough to drive it right.
I'm confused by all of this:
A: What company DOESN'T want you to keep buying stuff from them? Having things that are user-replaceable isn't just about helping the user, it also makes the systems significantly easier to manufacture, same as using a punched steel/riveted case with plastic fascia versus friction welded CNC'd Al-U-Min-Ium. Attributing their decision to make the devices non-user-serviceable strictly to a greedy money-grab is disingenuous to say the least. Do they want you to buy a new one from them? Yes, obviously. Did they also make the system non-serviceable because of some sort of weird fetish they have with making everything out of aluminum, glass and as thin as humanly possible? Also yes. The fact that you can't replace the hard drive in the iMac is just as much about that as it is about them being greedy SoBs.
B: The 21" iMac is 1920*1080, the 27" iMac is 2560*1440. What exactly is oddball about the 15" rMBP? It is 2880*1800, 4x the pixels of the sMBP's 1440*900.
C: My understanding is the the HD4000 is just exactly powerful enough, maybe just under. Definitely with no power to spare. But think on that for a second, it wasn't that long ago that the intel graphics in the OG MacBook (released 2006) could only handle 720p video, forget about 1080p. Now intel integrated graphics are driving a 2560*1600 panel that is using crazy scaling systems to simulate up to 3360*2100 (1680*1050 doubled) and scaling it back down to fit 2560*1600.
D
: What resolution would you want them to shift to on the 21" or 27" iMac anyway? Plus, they use dGPUs on the iMacs, so no need to worry about the HD4000 in them. Who the heck cares if it is standardized or not? For one thing, it seems like resolution 'standards' are made up as they go, and for another, Apple is using scaling algorithms to fit the content to the screen. They want 'retina' panels so that the image is less fuzzy due to the non-native settings, and to make whatever their target res choice fit better. You show me anyone other than Apple putting ultra-high resolution panels into their systems AND putting the effort into the software back-end to make them work as well as they do, and I will go buy a hat and then eat it. But the closest I can think of is the Asus ZenBook Prime 13" with a 1080p display, and they are just relying upon Windows' built in DPI scaling which is a bit of a band-aid solution, and not fully implemented in all programs.
All in all, it sounds to me like you are operating on either old or outright wrong information regarding what currently composes Apple's lineup and why it is that way. Which is nothing new, people frequently are when it comes to Apple. They still assume (for example) that you can only put iTS music onto your iPod/Pad/Phone (never been true), or that the music is DRM'd and will only work on iDevices (hasn't been true in years). They assume that Apple forces 8 year olds to work 120 hours/wk on whip-cracking assembly lines (no kids allowed, no OT anymore, and there are no whips, only weird beeping things). They cling to the idea of Apple using evil proprietary components and that they charge an Apple tax, yet let Sony and Lenovo slide for doing the same (once upon a time, it wasn't that crazy to see equally specced Thinkpads selling for more than MacBook Pros, and Sony has always been a little crazy about using proprietary stuff and charging a huge premium for it).