The key to Melbourne doing well in the finals is finishing as high up in the table as they can. Thus, they can afford to slip up in Week One.
Consider this - at the moment the finals would be:
1st v 8th - Roosters v Knights
2nd v 7th - Panthers v Broncos
3rd v 6th - Bulldogs v Warriors
4th v 5th - Raiders v Storm
Very hard to see the home sides losing, although Melbourne have beaten Canberra this year (at Canberra too?)
The second week of the finals (if all home sides win) would be:
Bulldogs v Storm at SFS (Winner plays Roosters)
Raiders v Warriors at SFS (Winner plays Panthers)
But if Melbourne beats Canberra in Week One:
Bulldogs v Raiders at SFS (Winner plays Roosters)
Storm v Warriors at SFS (Winner plays Panthers)
Based on this I would say they are good chances for the final four.
But it all depends on consistency. Look at Parramatta, flogged by 38 one week, winners by 70 the next.