Victoria hurried to victory with 6.4 overs to spare with captain David Hussey hitting 47 not out and opening batsman Aaron Finch making 38 not out.
The Bushrangers, who have completed their round robin fixtures with six points from three wins, now have to await the result of a match between Chennai Super Kings and the Eastern Cape Warriors in Port Elizabeth on Wednesday.
If the unbeaten Warriors beat Chennai, they will go through with Victoria, but if Chennai win the semi-finals places will be decided on run rate.
Chennai have the best net run rate of 2.57 but need the win to draw level on points. The Warriors are on 0.98 and Victoria's big win lifted them into positive territory on 0.03.
"Hopefully we can go a long way in this tournament because we are playing some good cricket now," said Hussey.
Wayamba reached 81 for two after ten overs with Mahela Jayawardene (51) and captain Jehan Mubarak (44) putting on 72 off 52 balls for the third wicket. But Mubarak fell to a superb catch at cover by Hussey and the Sri Lankan side collapsed ignominiously against the fast bowling of Siddle and James Pattinson and the medium pace of Andrew McDonald.
Nine batsmen contributed five runs between them, with six failing to score.
Victoria were outstanding in the field but Wayamba followed their poor batting by dropping two early catches and missing a run-out opportunity as well as allowing extra runs through misfields.
"That was probably our worst performance of the tournament," said Mubarak. "We need to do a lot of soul searching."