Rosetta 1 was introduced in Tiger (2005) and was no longer supported in Lion (2011). Thus it was an OSX function for 6 years...
Rosetta 2 was introduced in Big Sur (2020), and there is no reason to think it will not be around for a few years more.
Other benchmarks to consider are that Tiger was the first to support Intel hardware (no surprise), but then the very next version, Leopard, was the last to support PowerPC hardware. Two year overlap of legacy machine support, and the transition to Intel hardware was completed really quickly before that (1 year?). Apple Silicon has been here for over 2 years, yet the transition still has the Mac Pro hardware left on Intel.
The takeaway is that the Apple Silicon is going more slowly, so Intel support may linger longer than PowerPC did. Expectations may be for Intel hardware support for maybe a year or two past availability (maybe longer because "Pro"), and then Rosetta2 for 3-4 years after that, if history is any indication, tho I suspect a longer hardware support due to the transition, and Rosetta2 will feel like its stagnant by the time its removed. I see no reason for the APIs supported by Rosetta2 to extend beyond the version that can boot hardware (e.g. if Ventura were the last to boot on Intel, that'd also be the last developed API version for Rosetta). Already, as I understand it, Rosetta2 only supports obsolete x86_64 hardware without AVX support, while Ventura booting support requires AVX. That duality may already put Rosetta2 at a Monterey-level API..? They're maintaining 3 compiled versions of the system libraries, (arm64, x86_64 (rosetta/monterey/older), and x86_64h (ventura)), which I don't recall if PPC Rosetta did both 32 and 64bit or not. Dropping non-AVX from the system would take Rosetta and support for any intel binaries built against Monterey or older with it, similarish to Catalina dropping 32bit entirely. (longish brain dump)
