I'm going to have to say that, although 135 routes have not been announced, I highly doubt that Eagle will put the ERJ-135 into IND. If you look at Eagle's ORD operation, they use only the larger aircraft (145, ATR), and not the Saab (34 seater). I think that this is because of slot controls at O'Hare. Because they cannot schedule unlimited frequencies, they use larger aircraft and only serve markets that can support them. Because of this, I don't expect to see any ERJ-135s at ORD until slot restraints are removed.
As for ORD-IND specifically, I really think that there is little chance of Eagle bringing in a smaller plane. Before the ERJ-145, Eagle flew the route using ATRs, mostly 64 seat ATR-72s. When they received the Embraer, Eagle realized the value of IND as a business market and put RJs into operation here, but they retained a flight or two operate by the ATR to get those extra 14 seats. Now the schedule is dominated by the RJ, but from time to time there are still ATR fights. I really think that AMR is trying to balance the needed capacity with the desire of business travelers to fly on jets, and so I think that the ERJ-145 is the smallest plane we're likely to see in the market. I actually lean towards the belief that, if slot restraints are totally lifted at ORD, AA will probably take over the IND flights and operate mainline service just as UA does. I think that American just doesn't have the mainline slots at ORD at this time to operate the service themselves, so they releagte it to American Eagle.
Just out of curiosity, if you don't mind my asking, where do you go to school that brings you to IND?