There is also the chance of the US losing a lot of its power through various means (ie. Dollar losing reserve currency status, US military being tested by China and losing etc.). If this happens, they may be forced to cut Israel loose. Israel has no other solid allies and so they will flounder for a while but eventually sink because once the US is out others will be free to begin economic sanctions and the country cannot survive that indefinitely.
In both of these scenarios, the lobby groups become less effective and possibly get defeated. Long term we are moving towards a world where lobbies become less powerful. Its going to take decades though.
The "hard left" sees Israel for what it always has been: A settler/colonial state. Israel will continue to push propaganda to bury this but the truth can never be erased.
Who knows, maybe it never happens. If climate change brings about tens of millions of new refugees I don't think people will have that much time/energy to the so called Palestinian refugees anymore. They will have to get along like everyone else.
There is a possibility of a significant economic decline in the US caused by climate change such that the US will not be able to help Israel anymore just due to lack of resources.
Most of the countries in the region will be swallowed by the desert and that may include Israel. Even though Israel is at the forefront of mitigation technology, it does not seem like it is enough from what I have seen.