True, but in case of a fork electrum might only work for one of the possible bitcoin forks.
that's not true. The Electrum client will not be affected by the max block size change.
Maybe I was not clear. I was referring to the scenario where Bitcoin XT emerges as an alt different from Bitcoin, with an identical historical blockchain. In this case I would assume you (and others running Electrum servers) would have to decide which coin to follow.
Is this a wrong assumption?