That's the way I read the language also; the 25th 787 ends the fence.

Charleston and Everett are starting to produce non-retrofitted 787's so I'd guess far less than 5 years. According to this blog, 7 UAL 787's have been delivered, with 1 aircraft in flight prep, so how long for the other 17 jets?

All 8 of these aircraft should be in operation by the end of this month:
N20904, N26902, N26906, N27901, N27903, N27908, N29907, N45905