My guess is that it's 2025-2027 for dropping intel support based on their current support approach, and I expect we'll get a year's notice like we did on the kext depreciation.
I'd guess that Rosetta 2 will last at least a few years after we lose intel support in the OS itself, so figure 2027-2030 for that.
If we're lucky we might see 'extended support' for the last Intel version, but Apple's been pretty harsh about that, so I wouldn't count on it. In any case, if my timeline is right, that means that as early as 2026 and no later than 2028 every intel machine will be unsupported, and unpatched. At that point, wiping them and installing Linux will be the only real option to stay secure. Note that Windows 10 won't be supported after 2025, so that's not an option.
