Is a new Mac good for Pro Tools and older plug-ins?

[Infiltrator]

Just considering a new mac for PT 10. Are the latest mac OS systems out compatible with either pro tools 10 or pro tools m powered 9? And would m-audio make sure all drivers for my firewire project mix interface is compatible? Because theres no way in chance im spending on an apogee interface when i spent 6 grand on an eventide H8000FW to be able to convert anything with super high end conversion - and to run everything optical out of that to my m-audio sound card.

Also, will all this Native Instruments stuff from years back be up to date for the latest Mac OS systems? For example - Absynth - some sessions have instances of both Absynth 3 and Absynth 4. I hope when opening sessions that these instances will open fine.

What about other plug-in companies? Are they ensuring that their older plug-ins will be up to date with the newest Mac OS?

And is a Mac Pro quad enough? (my sessions are not too too complex, and other than maybe some NI effects, plug-ins will not be processed by the computer other than only Superior 2 drums... But audio processing plug-ins will mostly be processed by UAD firewire and Virus Control via USB for my main synth).

Thanks Much.