Developing <i>for</i> 32-bit Linux still makes sense, for extremely constrained embedded use.  However, developing <i>on</i> 32-bit Linux no longer makes sense.<p>And supporting 32-bit in something like the Android SDK does actually add effort and cost: storage for 32-bit packages, build time for 32-bit packages, additional continuous-integration server time that may slow down the development cycle, etc.