I don't think that really holds. I had a cheap 2048x1152 23" monitor in 2009. Excepting very rare 2048x1536 15" laptop displays, it was comparable in pixel count to the previously-top 1920x1200 laptop resolution. The iMacs have had a 2560x1440 27" option since 2009 and I'd expect the next update to go higher. There have been 2560x1440 or similar 30" displays for a while, my boss was using one in early 2009 or so, 2880x1880 or higher can't be far off.

Since you're comparing with "most desktop rigs", you should also remember that most 15" laptops are 1280x800 or 1440x900.