You may be interchanging 2 different things.
1. Slammers has 2 teams in ECNL (they call one LAFC Slammers and the other Slammers FC). These teams are in the same league-- but LAFC is always the higher of the 2 (look at the standings). I would expect that will continue. So there are 2 teams in the same league.
2. Dof3 probably has it right for the ECNL Regional League (ECNL 2). There will be an LAFC Slammers and Slammers FC team in this league, too. So 2 teams at this level, too.
Look at the 00/01 level this year for an indication of what will likely happen next year with their teams-- they have 2 teams in ECNL and 2 in ECNL Composite (believe the same coach-- AG-- coaches the 2 Composite teams this year, even though one is call LAFC Slammers and the other Slammers FC). Sounds like the ECNL Regional league will replace Composite at the older age group (01/02 next year), and then they will take this new league down to younger ages. I cannot imagine Slammers having 4 teams in the 'regular' ECNL level.