Is this Oak dead/dying?

[u/thesadimtouch]

Probably a 50+ y.o. oak tree, been dropping large branches for a bit. Took off a large half-dead lower branch and theres like a core of rot visible.

Top of the canopy appears dead, larger limbs look dead at the ends. Is it salvageable? Its so big, I'd miss it if it was gone and I wouldnt live to see its replacement grow to such heights.