If these lawyers wanted to go after the devs the only leg they could possibly stand on under US law would be trademark tarnishment[1].
In any case it could possibly be defended as parody, but only if the fact that the developer didn't use the IKEA name doesn't end the lawsuit sooner - which however would make it a really obvious parody.
[1] 15 U.S.C. § 1125(c) https://www.law.cornell.edu/uscode/text/15/1125#c