When the Hitachi trains were built in the early 70s, it was before the days of dot matrix displays. Destination rolls weren’t easily changed, so they included a few places they thought that might one day get rail services.
Forward planning, much of it in line with the stated rail extensions in the 1969 transport plan.
Here, courtesy of an old railways book I have, is a list of destinations which had been added in anticipation:
DEER PARK WEST 
SOUTH MORANG 
EAST DONCASTER 
Interesting omissions include Cranbourne (opened 1995) and Warragul (a few suburban trains went out that way during the 90s).
 Werribee — was electrified and got suburban trains in 1985.
 Sunbury — No electric trains yet, but funded and expected to open in 2012. Controversial because some locals would prefer to keep their V/Line trains, though I think the project brings numerous benefits.
 Deer Park West and Melton — Electrification and duplication from Sunshine to Melton is included as part of the Victorian Transport Plan, but is not currently funded.
 Craigieburn — Eventually got electric trains in 2007.
 South Morang — Funded and expected to open in 2013. Controversial because of the astronomical cost, partly explained by the project including lots and lots of other stuff. Interestingly the official government information now appears to be devoid of an expected opening date.
 Doncaster — Despite bridges on the Eastern Freeway being specifically built to accommodate a train line, it hasn’t eventuated. A big upgrade to bus services, under the name DART (Doncaster Area Rapid Transit) is about to start.
 Mulgrave — The State Coalition has pledged to do a feasibility study of the line to Rowville (including Mulgrave) if it wins the state election, one of its few policies announced so far.
 Baxter — Not planned, but the PeninsulaLink plans do include provision for expansion of the existing line underneath part of the freeway under construction. Extending to Leawarra (where Monash’s Peninsula campus is) and Baxter makes sense, if only to move the train stabling and massive car park out of Frankston, which can be redeveloped as part of the multiple CBDs strategy.
 Mornington — Gone backwards. The station and some of the train line that were there have been demolished/ripped-up… the only indicator left is Railway Grove.
Going back further, here are some that were on the blue (Harris) trains:
The red (Tait) trains appear to have listed only stations which today get suburban trains — or did at the time (St Kilda and Port Melbourne, for instance).
 Trains once ran here, though I don’t think they were ever electric trains.
- Source: Electric Railways of Victoria”, by S.E.Dornan & R.G.Henderson, AETA 1979
- The full lists that I once laboriously typed up and posted to Usenet — and include a few stations which are no longer used to terminate trains, such as Glen Huntly and Westona