I highly doubt this will affect Diablo in any way, outside of them changing the leasing cost or outright suspending their lease for no reason.
The Alpine Slide will never return. The world is a different place even from 15 years ago when I was a season pass holder. Back then, you wipe out on that sucker and learn a life lesson about trying to show off. Nowadays, our culture has shifted to dollar signs, and every crash would be another lawsuit in the works. Also, Mountain Creek and Diablo have so severely modified the terrain it once occupied, it would never make financial sense to rebuild the thing.
It's also not like they can take any Diablo property and build condos. Remember, the freeride park cris-crosses active ski trails, and I doubt they would eliminate half the mountain on a risky venture.
The only hope is that they continue to build on what South has been turned into, a high-quality terrain park with a draw all it's own. South Peak under Great Gorge's management was a complete dud, barely worth venturing over to.
Only time will tell.
P.S. I agree that it would be awesome to go back to the Action Park days, but there is no chance they'll go back and make all the current shit dangerous again for nostalgia's sake.