As things stand, the 92 clubs in the upper, "professional" echelons of the English football pyramid are divided into four divisions. There's the 20-team Premier League, once known as the First Division, followed by three 24-team divisions of the Football League (the Championship, League One, and League Two). All four divisions deal with their specific flavor of fixture congestion, with most clubs involved in at least three, some four competitions leading to tons of midweek games and inefficient scheduling (midweek games may be well attended in the Premier League, but the same can't be said in lower division). Reducing this strain on players, fans, and administrators, is one of the aims of the Football League's new proposal to add a 'fifth division'.
There are of course other ways to accomplish these goals (do we really need two national cup competitions, for example?), but for now, this 'fifth division' plan seems to be the main idea that's being entertained.
The new division, proposed to start in the 2019-20 season, wouldn't drastically increase the total number of professional clubs as all five divisions would be set at just 20 teams. Still, it would mean the addition of eight new teams to the ranks, which would include two promoted from the (semi-pro) National Leagues, as well as six more, probably also from non-league, though the prospect of adding Celtic and Rangers wasn't immediately ruled out.
"The whole discussion can be had. But I suspect the wider this gets drawn, the harder it would be to deliver to our clubs and the rest of the stakeholders in the game."
-Shaun Harvey, Football League CEO; source: PA via Eurosport
Apparently even harder than including two Scottish teams would be the idea of introducing B teams into the league structure, which has been categorically ruled out. But according to the PA report, B teams could possibly be entered into the FA Trophy (i.e. Johnstone's Paint Trophy), which could perhaps one day pave the way to similarly beneficial structures for player development seen in other major European leagues like Spain.
Final decision one way or another is not expected until June of next summer (2017) on this issue, so the various stakeholders (Football League clubs, The FA, and even the Premier League) have plenty of time to discuss and negotiate and figure things out.