I guess its possible that you could have a guitar that would sustain for ages, but with the majority of the energy being 'released' at frequencies inaudible to the human ear, which would actually make it appear to have little "perceived sustain". And resonance would indeed have something to do with that 'perceived sustain'.
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According to this website, "Quality factor” Q = sqrt(C × Cc) / d where C and Cc are the speed of sound longitudinally and across the grain, and d is the density of the wood. "
The 'Quality factor' is basically what determines somethings 'sustain' (be that pleasing, audible sustain or otherwise), so If anyone were ever to try to actually quantify the sustain of woods, this may be a starting point. I couldnt find a table of typical Q values (or typical speeds of sound propagation) for different woods in a quick google search, but there may be one out there.
Of course theres a lot more too it than just the Q of the wood you choose, but as I said, it is perhaps a start.
Someone fund me and maybe I'll do this as my PhD thesis
Seriously though, it would be cool if you did.
And also, if anyone were to try to measure the speed of sound in woods, there are some ideas here of how it could be approached experimentally, and by the look of it, not too expensively.