I was pleasantly surprised to receive an email from SQ today informing me of a change with my seating arrangements on my SIN-MEL SQ227 flight in November since my pre-selected seats "...are no longer valid due to a change of aircraft from B747-400 to Airbus 380." 
And there was a second email from SQ pointing to this media release of 15 July 2009 (http://www.singaporeair.com/saa/en_UK/content/local/AU/before/LocalPressReleases/071509.pdf):
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The daily A380 flights will replace an existing daily Boeing 747-400 service to Melbourne. SQ227 will depart Singapore Changi Airport at 2100hrs and arrive in Melbourne at 0610hrs the next day (0710hrs from 4 October 2009 due to daylight savings). On the return leg, SQ228 will depart Melbourne at 1550hrs (1650hrs from 4 October 2009) and touchdown in Singapore at 2140hrs. "

And there was a second email from SQ pointing to this media release of 15 July 2009 (http://www.singaporeair.com/saa/en_UK/content/local/AU/before/LocalPressReleases/071509.pdf):
"
Australia becomes first Singapore Airlines market to boast dual superjumbo ports
[FONT=FMPDB B+ Laudatio BQ,Laudatio BQ][FONT=FMPDB B+ Laudatio BQ,Laudatio BQ]From 29 September 2009 customers travelling between Singapore and Melbourne will enjoy an unrivalled flight experience on Singapore Airlines’ superjumbo Airbus A380. When the new service begins, Melbourne will become the second city in Australia and sixth city in the Airline’s network to receive the A380 – highlighting the ever expanding services being provided to Australian customers by the international carrier. [/FONT][/FONT]
....
The daily A380 flights will replace an existing daily Boeing 747-400 service to Melbourne. SQ227 will depart Singapore Changi Airport at 2100hrs and arrive in Melbourne at 0610hrs the next day (0710hrs from 4 October 2009 due to daylight savings). On the return leg, SQ228 will depart Melbourne at 1550hrs (1650hrs from 4 October 2009) and touchdown in Singapore at 2140hrs. "