It doesn't really matter whether you relegate back to Div IV again. If you end up in 7th or 8th place etc, you'll have a high pick in the draft and you can draft a good draftee (supposedly + if you're lucky). In addition, even if you relegate, you'll probably promote do Div III again and once again you can receive the promotion bonus etc. But personally, I'd try to stay in higher Div as much as possible.