Depends on the results they are looking to achieve. If they're shooting for top 10 finishes and the occasional podium, I think they will stay around for a longer time. Obviously they aren't coming into this thinking they will snatch a World Championship. According to the article though, their participation in MotoGP will be the same as in Moto3. I, think we'll see KTM lending strong support to strong privateer teams. If what the article says is true, KTM could honestly hang around for as long as they like. Supplying teams with machines and then doing the R&D alongside the teams would mean they get to develop at their own pace. However, if multiple teams decide to run KTM machinery, we may see KTM being able to develop rather quickly. Would be kind of in the same vein that Ducati is shooting for next year, in that they are running six riders. If KTM get the consumer base, I'm sure they will back them.
I, think if we can start seeing 30+ grids it can only mean better racing for everyone. The paltry 20 or so riders at the moment is o.k. at best. Look at Moto2 & Moto3. Tons of riders are vying for wins.
With the potential "reset" we are going to see in 2016. Hopefully it means the competitions tightens up and produces more than just one guy winning all the races.