Can't see it being a single 12 team league. I know we used to do that in old HPL days (and maybe once in the BNL?) but that was when we had longer Autumn Cup tournaments and Playoffs. And even then we still had to pad out the season with Southern Cups etc.
Budgets are based around a 60 game season, whilst one single league would be either 44 (too few) or 66 (too many). Plus the whole point of the conferences was that it helps the Scottish teams with games against more even teams and cuts down on travelling for everyone. The fact that they were going to keep the conferences for an 11 team league (how I don't know) suggests that it will almost certainly be conferences and almost certainly geographical based. Which leaves us with two options:
2 Conferences:
Gardiner: Belfast, Braehead, Dundee, Edinburgh, Fife, Manchester
Erhardt: Cardiff, Coventry, Guildford, MK, Nottingham, Sheffield
This would arguably give Belfast a big advantage in winning the league title. Although it might not be good for them financially as they get their biggest crowds against Cardiff, Nottingham and Sheffield
3 Conferences:
Scottish: Braehead, Dundee, Edinburgh, Fife
Northern: Belfast, Manchester, Nottingham, Sheffield
Southern/Fire: Cardiff, Coventry, Guildford, MK
This would arguably gives us an advantage, although with Coventry's improved attendances they might have a better budget next season. And who knows how competitive MK and Guildford will be. It would be toughest on Manchester but the extra games against Nottingham and Sheffield might bring in extra revenue.
Both conferences will work though with playing your conferences rivals 3xhome and away and the others 2x home and away. So it won't be the huge difference it is now.