It won't in the foreseeable future.
The question is when pro-Palestinians will be a bigger part of the Democratic base then Jews are. I expect a vocal pro-Palestine block to develop within the Democratic caucus in the next 10-20 years.
I really doubt that; you'll notice, the trend over the past few years has been for
more public approval of Israel's actions, not less (in 2000 pro-Israelis were at about ~60%, now they're ~70%; pro-Palestinians have remained about the same at ~20%). If anything, the logical trend is that pro-Israeli groups become stronger, not the reverse.