I really don't understand why this "32-bit gone" myth is happening. It was poor wording at least. Debian doesn't even support the ancient 32-bit sparc CPUs. Modern SPARC ABIs (post 1997) require 64-bit CPUs even when running in 32-bit code, it's like x32 ABI in x86 land.
SPARCv7, SPARCv8 = old 32-bit CPUs, Linux kernel barely supports them now
SPARCv9 = modern (post 1997) 64-bit CPUs, Linux and GCC supports them just fine.
And just so we can finally kill this rumor dead:
GCC still supports the 32-bit ABI:
With -mv8plus, GCC generates code for the SPARC-V8+ ABI. The difference from the V8 ABI is that the global and out registers are considered 64 bits wide. This is enabled by default on Solaris in 32-bit mode for all SPARC-V9 processors.
So no, you don't need to rebuild everything as 64-bit binaries, or should I say, rebuild under LP64 model. That wouldn't even make sense and would hurt performance. Please refer anyone who believes this to this message.