Now newsmanhoss did say that rumored information from front line people is notoriously unreliable. I'm sure he doesn't believe everything he hears!

That being said, AirTran currently has six gates (C20-25), and uses C15 regularly. Their current schedule can work with only six gates, but for most of the day then can get by with just three gates

Here's MKE optimal gate utilization with the current AirTran schedule.

Gate 20 used regularly most of the day
Gate 21 used regularly most of the day
Gate 22 used regularly most of the day
Gate 23 not used between 8:25am and 3:30pm
Gate 24 not used between 8:30am and 5:50pm
Gate 25 not used after 8:35am
Gate 15 not used

Now this is optimal gate utilization, not accounting for any irregular operations or delays. And of course in actual practice airlines with more than a gate or two tend to mix up usage to absorb early arrivals and departure delays without conflict. But it does show that AirTran could get a lot more flights through their existing gates.

There are two practical issues that limit what they can do with their existing gates, however:

(a) Banking
AirTran banks many of their east-west flights pretty tightly. So while there's room to add quite a few more flights, where they very quickly run into trouble is if they want to (for example) add a several flights to the current banks. So while they might want to add more feeder flights from Philadelphia, Dayton, Raleigh, Dulles, Rochester, etc, they can't arrive at 8 am or 6 pm to dovetail with the west coast departing banks because there are not enough gates.

(b) Practical time logistics
When it comes to adding flights at Milwaukee, the times not only need to make sense at MKE (based on the slack gate availability I'm talking about) but they need to make sense at the other end, as well. The easiest way to illustrate this issue is to talk about west coast flights. For practical purposes, flights arriving MKE from the west coast have to come in after 1pm. And if they are going to feed eastbound flights, they can't come in later then 7pm. So while they may want to add more flights to/from the west coast, and there may be gaps in gate usage during the day, the west coast arrivals (other than red eyes) are necessarily going to be in that 6 hour window. There are similar (if less broad) practical issues east coast flights. For example there's a LGA-MKE that arrives about 7:45am. There's plenty of gate space open in MKE at 9:45 to have another LGA-MKE arrive then. But it would leave LGA at about 8:30am. That's generally too early to have that plane already fly XXX-LGA to be ready to leave LGA at 8:30 for Milwaukee. So to have an LGA flight arriving MKE at 9:45am, it would have to sit around idle until 8:30am at LaGuardia, which is not very good for utilization.

So...while there is potential for quite a few additional flights at MKE based on optimal gate utilization, that doesn't mean they can necessarily use those gates up to their maximum potential. If they add more short-hop markets and offer higher frequency, they have a better shot at approaching full utilization. So a lot depends on the types of flights they intend to add when it comes to guessing what they can get further out of their existing gates.