Rumour has it that after the Mordialloc sidings have been redone over the next few months that during the off peak period every 2nd train will to Frankston will terminate at Mordialloc and go back to Flinders St. By my reckoning that will mean a 20min service between Frankston and Mordialloc between 9am and 4pm and i don't reckon the locals will be too pleased. If this is true i would expect the new government to knock it on the head since all the sitting Labor members between Mordialloc and Frankston lost their seats at the last election, with a big reason being the poor performance of the Frankston line.
I don't see why they would introduce a down-graded service from 10 min to 20 min (or even 15 min to 20 min). The more likely reason is to turn back trains at Mordialloc during peak, to reduce the number of rollingstock needed as well as split the loading (i.e. forcing people who live beyond Mordialloc to take an express).
Also, Upfield will not receive any service upgrades for a while due to local opposition, especially with the council who dislike trains delaying cars at the large number of level crossings.
Perfectly agree with your point regarding Frankston. I doubt (although I am no expert) that following Metro CEO's desire for a "truly metro system" with 10 minute frequencies, that we would go backwards...
I don't know about you, but I trust Andrew Lezala's call, it would be a PR disaster to go back on such a big "vision", even if he didn't make that comment, going backwards is definitely not the answer, and commuters far and wide would be quick to bite at such a major change.
However , knowing the delays the line has been experiencing lately, maybe cutting back some services until some improvements can be made could be Metro's vision... that is, "we tested this for almost 6 months but the service is still bad, we need to try something else before we can re-introduce services".
But to be honest I don't even really support that statement which I came up with

haha...
Also, Azn_dj, I have looked a little into the Upfield line, and many people I know personally and from opinions online+the news etc is that more services=good.
I doubt ANY community in the city would be against more frequent train services just because of level crossings...
You don't hear people in Clayton/Springvale saying "we want less trains on the Pakenham line to stop the boom gates staying down", instead you hear for calls of grade seperations (i.e. the more feasible option)
Upfield residents (which sort of makes up the voice of the council) in my opinion would be grateful for any increase in services
If you look at the Coburg re-development plan, Council advocated to the state government to sink the Coburg rail crossing underground to create a better entrance into the retail hub. (I think though this is now history, with the cost being a main factor, but I was just trying to highlight Councils point of view)
Cheers
EDIT: After having a look at the previous poster who provided several links which de-bunk your claim, I am interested in what made you say that AZN_dj.
Maybe we are missing something/mis-interpreted, don't want to be quick to bite the bullet!