I have flown out of IND to MCO 2 or 3 times a year since 1992. I go Dec., Jan. and/or Feb.. As of now, three airlines fly nonstop from IND to MCO; NWA, SWA and AirTran. All I can do is go on past experiences, who knows what will happen with fuel prices, etc.. I always thought anything around $200 is a good fare, but if a person stays on top of the airline pricing you can usually do better, than that from IND. I usually wait until SWA comes out with their fares for my dates and then check all three airlines for prices. I keep an eye on them and buy when the fare comes down. It's like the stock market it's hard to buy low. I don't like the cattle call boarding of SWA, so rarely fly with them, but the other two carriers usually match or are lower than SWA in IND.
The lowest r/t cost from IND to MCO that I know of someone getting was $88 r/t(taxes and fees included) on SWA during August of 2005. This past late Jan. early Feb. I flew r/t on NWA for $117(everything included in price). I have found these to be unusual fares to get. I would say a fare of around $150 r/t is very possible. Since you are flying Sat. to Sat. I'm not sure how low the prices may go. I'm retired and can and do spend time trying to get good prices and am flexible on dates of travel. For some people it isn't worth the time spent to save a few $$$ or they don't have the patience.
Good luck. Someone else might give their experiences.