"The lottery will be tomorrow" is also good in English; I have a suspicion that 'be' in English is usable for a variety of more active/eventful situations than 'ειναι' in Greek (eg 'I haven't been to the casino in four months!')
"The lottery will be tomorrow." I believe γίνει means "to be". I see no reason for the word "held". It is not needed by the English and is not present in the Greek.