The pro tools (like Pro Tools) are usually the tools that are being ported first. It was the same with all the other transitions.
If not, there will be Universal 2 binaries with both x64/Intel binaries for a while and an emulation mode for legacy binaries. Underoptimized at first? Maybe, but they work well enough and performance catches up eventually -- the transition is over 2 years. Same situation as before. Software that work will continue to work on existing and new hardware for a while. Nothing is going to stop working the moment the new processors come out.
We've seen all this happen before (m68k - PowerPC - Intel). And it's really not a problem.
If not, there will be Universal 2 binaries with both x64/Intel binaries for a while and an emulation mode for legacy binaries. Underoptimized at first? Maybe, but they work well enough and performance catches up eventually -- the transition is over 2 years. Same situation as before. Software that work will continue to work on existing and new hardware for a while. Nothing is going to stop working the moment the new processors come out.
We've seen all this happen before (m68k - PowerPC - Intel). And it's really not a problem.