A new development blueprint includes improvements to the main Edinburgh-Glasgow route which would clear the way for six trains an hour in each direction – or one every ten minutes.
It could follow the current £750 million upgrade of the line, which is being electrified for faster journeys between the cities in the biggest project of its type for 25 years.
The first electric trains are due to start operating on 11 December, with a new Japanese-made Hitachi fleet being introduced from next year.
Platform lengthening at Queen Street Station in Glasgow will enable seven-carriage trains to run, compared to the maximum six at present.
They could be further extended to eight coaches.
Journey times will be cut from some 50 minutes to 42 minutes by 2019.
The potential further expansion move to increase train frequency from four an hour is seen by experts as evidence of the strength of the country’s rail boom.
ScotRail’s passenger numbers have increased by one- third to more than 90 million a year over the past decade and are expected to reach 139 million by 2025.
Track owner Network Rail’s new Scotland Route Study prooses that a key junction on the route be upgraded to provide space for the extra trains.
The work at Greenhill, west of Falkirk, where the line to the north branches off, is estimated to cost £50m to £100m.
If approved, it could be built between 2019 and 2024, with the junction becoming “grade separated” by adding flyovers so trains would not have to cross tracks when switching between the two lines.
Running six trains an hour on the line was part of the original £1 billion electrification project – known as the Edinburgh Glasgow Improvement Programme (Egip) – before it was slimmed down in 2012 to save money.
Ministers opted instead to run longer trains to provide the extra seats required to cope with growing demand.
A rail expert told Scotland on Sunday it was very significant that higher frequencies could be back on the agenda.
They said: “Growth is really strong to be considering this expansion, which is a sign of confidence in both the railway industry and the Scottish economy.
“Six seven-coach trains per hour is a hell of lot of seats.
“It shows the strength and further potential of Edinburgh and Glasgow as a combined urban economy in the future.
“It also demonstrates the scoping and planning and phasing of Egip wasn’t far off the mark in that there’s an obvious set of next steps to get even more capacity out of the network.”
The Scottish Government’s Transport Scotland agency, which is funding Egip, confirmed that increasing train frequency was still an option.
Its spokesman said: “The Scottish Government remains fully committed to the Egip objectives, including infrastructure for six trains per hour, which could be delivered in later phases.
“Decisions regarding the timing and specification of future phases would take into account future rail demand and capacity requirements.”
But a transport think tank questioned the need for more trains on the line.
John McCormick, chairman of the Scottish Association for Public Transport, said: “A grade-separated Greenhill junction would improve reliability, but as the Network Rail document says, would also give the potential for six trains per hour on the Edinburgh-Glasgow line.
“However, as lengthening the trains to eight-car – enabled by the Queen Street reconstruction – is being undertaken to provide extra capacity, there is no immediate need for six trains an hour.
“Also, electrification of another Edinburgh-Glasgow line, via Shotts, which is due by 2019, will allow a faster electric train service between Glasgow Central and Edinburgh, which is likely to attract some passengers from the main line.”
The Network Rail document also includes another shelved element of the original Egip scheme, to divert some trains via another line for part of the journey to reduce congestion in Edinburgh.
Some services would run from Winchburgh, near Linlithgow, then via Dalmeny, near the Forth Bridge, to enter the capital on the Fife line.
That would avoid trains having to cross tracks around congested Haymarket Station in the west end of the city.
It would also provide an interchange for passengers travelling between Glasgow and Fife at the new Edinburgh Gateway Station at Gogar.
The station, which is due to open in December, will also enable travellers to switch to trams to nearby Edinburgh Airport.