This rumour of Impulse 737s is an interesting one. Up until a couple of weeks ago, Mel-Ool and Syd-Ool schedules showed some flights operated by 737s, but claimed to be operated by Impulse Airlines. This has since been fixed up, but maybe it is an indication that it will happen eventually???
This rumour would fit in with the other rumour about 737s taking over the current 717 routes, and the 717s going on to new routes.