You are correct it is 1-2 years compared to 5 years, and we don't know the productivity of the FA's. The productivity of the FA's is a big question mark, and we will no doubt see productivity gains from them.

It is possible there were productivity enhancements of up to 10-20%, if that is the case then they could handle significant fleet growth while still shrinking there flight attendant employee group, but not for very long even with those rates.

Regardless their reasoning, the trend regarding the net loss of flight attendants does not seem to me to point to significant short term growth, making Horton's 2500 more difficult (not impossible ) to obtain.

In order to make 2500 work they need over 70 additional aircraft above current projections on the property in the next 5 years. That could be done by holding onto the MD80's much longer.

The following is the spreadsheets that build the projection model for AA if anybody has further insight on them please feel free to let the site know.
American Airlines -Supporting Spreadsheets | Audries Aircraft Analysis

The other alternative to make this work is a significant loss in current Pilot productivity with the new contract and new rest rules.

Both options to make the math work do not seem very plausible, but then again maybe they do want to hold onto the MD83's for longer.