Sending it to the local waste-to-energy plant and buying new stuff, three times, doesn't necessarily have to be meaningfully worse for the environment than buying "solid" stuff once, then moving it twice over a long distance (in a relatively inefficient, one-off move rather than large-scale logistics).

Consider if you're moving cities (lets say 250 miles) and going from a 10' van to a 17' van (with the assorted Ikea furniture) moves you from 12mpg to 10mpg - that's 20 gallons of gas to 25 gallons of gas. That's an extra 45 kg of CO2 emissions.

Buying new furniture at the new destination then is a smaller incremental cost of going to Ikea anyways.

And while I'll admit that this is a very simplistic analysis, the corresponding assertion that doing this is a larger carbon footprint may fail to take into account some nuances.