The Gers secured their place in the second tier last month, but they face a difficult task of gaining promotion for a third successive time next year.
Hearts will join Rangers in the Championship following their relegation, while any of Hibernian, St Mirren, Kilmarnock, Partick Thistle or Ross County could follow.
"Absolutely, the prospect of a big club like Hibs coming down worries me," McCoist is quoted as saying by STV Sport. "No-one has a God-given right to win games. I've already said it will be a hell of a competitive and interesting league.
"We don't know who will be coming down and there is a few twists and turns to come out of the next two or three weeks, which I'm looking forward to watching.
"Hibs have been mentioned but there are three or four of them down there fighting to avoid that play-off place, so it will make it really interesting for our league next year whoever plays in that playoff and ends up coming down."
Rangers still have three fixtures remaining this season, starting with a home clash against Ayr on Tuesday night.