No, it will not be deleted.
Yes, recipient will see it when it will deliver to recipient's inbox, and if they click on message request inbox, but they will not able to click on sender's name as sender has deactivated the account, means sender's name will be there without hyperlink. When sender reactivate their account hyperlink will be activated to the name.
Deactivating account will not delete anything. If you deactivate your account:
- You can reactivate whenever you want.
- People can't see your timeline or search for you.
- Some info may remain visible (example: messages you sent).