Boles said that attendance at last month's event was "the highest in four years" with 67,648 on Sunday and a three-day total of 145,558, but the track's projection for '16 "could not guarantee financial success given the expectation of an increased sanctioning fee." Indy Star
Following the removal of the Mazda Raceway Laguna Seca from the MotoGP schedule in 2014, the Red Bull Indianapolis Grand Prix became the only summer MotoGP event in North America for the last two seasons. This caused both financial and logistical challenges that no longer made the event viable for the foreseeable future. Ultimately, removing the Indianapolis race became key to Dorna's efforts to expand both the number of events it hosts and the geographic diversity of its schedule.
This makes room for another 4-wheel race at the track. That race should be the Indy 400 IndyCar season finale. Of course that makes too much sense so it will never happen. The family has tried everything except swamp buggy racing. All have failed (including the NASCAR Sprint Cup race which is failing) but they refuse to add the race that makes all the sense in the world – a season finale for the IndyCars at the home of the IndyCar series — the Indianapolis Motor Speedway.