I've explored some of the roads from Capay Valley west up into the hills. They have all had locked gates. There used to be a fire lookout up where the radio towers are. I don't know from which side that area was accessed from, but I'm pretty sure it's an exclusive club to get up there.
I highly doubt there will be any access across Monticello Dam. Both from a security standpoint and need. The east shore of Berryessa is easily accessible from Highway 128, just east of the bridge across Cache Creek downstream of the dam....if you have a key. Check out Google Earth, you'll see lots of roads and trails up there. It is almost all private property on the eastern shore, north of Monticello Dam (a little landlocked BLM thrown in for good measure). I don't see public access happening at any time in the future.
"I don't know what you do, but I know what I do, and I don't do that." --Uncle Doug, R.I.P.
"Without the possibility of death, adventure is not possible"--Reinhold Messner