Looks like USCIS error.
Your H1 also could be approved.
you: Hi there, I have got my spouse H4 approval on 1/28 . The problem is H4 approved for future date - Our last VISA end date was 7/1/2018, instead of giving 7/2/2018 as validity start date, USCIS has given 7/2/2019(both in notice and new I94), which is future date.
Question: What is the validity start and end dates on H4 visa.
Did you check the I-94 details online? What are the dates there?
I have placed a e-request in typographic error in USCIS website, Is it sufficient? or Do I need to talk to USCIS customer service?
Ans: Did you take a screen shot of this filing?Do you have any other proof of this filing? Keep it for your records.
I would strongly suggest to make an InfoPass appointment and present your situation with USCIS officer directly in person. And ask them a receipt of that visit with detail to prove that you have done your due diligence.
Since Approval is for future date, continuing stay in US will cause any issue?
Ans: Technically YES. But since the approval is a potential error by USCIS and you have acted immediately (as I said in above answer for 1:), you may be logically safe.
I am still waiting for my H1B approval, but I have got H4 approvals, Can I safely assume H1 is approved as well?
Ans: You wont get the H1 Approval copy as its being owned by your employer, not you. Your employer or attorney gets the approval. Your H1 is expected to be approved with the same dates of H4 mistakes(if you are lucky, I will be wrong).