Gers will be joined in the second flight by already-relegated Hearts, but it is the prospect of a number of other major sides also lining up against his team which has got McCoist concerned.
Any one of Hibs, St Mirren, Kilmarnock, Partick or Ross County could end up in the end-of-season relegation play-offs, while Dundee and Falkirk could miss out on automatic promotion to the Premiership after Hamilton took over as the Championship leaders.
And coming up from the third tier alongside Rangers could be Dunfermline as they aim for promotion via the League One play-offs.
McCoist said: "The prospect of a big club like Hibs coming down worries me.
"I've already said it will be a hell of a competitive and interesting league.
"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 goes down."
With the off-field saga at Ibrox refusing to die down amid rumours of impending cuts to McCoist's budget and supporters ticket boycotts, the boss is keen to put a "testing" campaign behind him.
"I'm looking forward to my holiday, if that's what you are asking me?" the club's all-time record scorer said.
"But we've got three big games left and, even before that, a lot of planning to do for next season.
"We have to look at pre-season, squads, players - a lot of work is still to be done."