UPDATE: The Commentator is calling it a hoax:
Prof. Hawking trip NOT cancelled due to Israel boycott
Professor Hawking’s spokesperson has confirmed that he will not miss the conference in Israel due to a boycott, but rather because of health reasons
However, a Cambridge university spokesperson has confirmed to The Commentator that there was a “misunderstanding” this past weekend, and that Prof. Hawking had pulled out of the conference for medical reasons. A University spokesman said: “Professor Hawking will not be attending the conference in Israel in June for health reasons – his doctors have advised against him flying.”
NOTE: This is the kind of evil mindset arrayed at the Jewish state, using a man’s illness for their own advantage and the media willingly buying into it.
UPDATE II: Algemeiner now reporting that the story is true.