Hi,
I think all these are correct.
1.I hope you had a great summer.
2.I wish you had a great summer.
3.I hope you have a great summer.
4.I hope you will have a great summer.
What is puzzling me is that I heard that you should use present or future tenses with the sentences with the word 'hope' and a past tense with the word 'wish'. And no. 2 doesn't fit that recommendation but people seem to say it is correct. Why? If is correct, I see no difference between that and no. 1.