Dobson will be the best WR on the team next year in my opinion.
I would expect to see –
Y-WR – Edelman
X-WR – Dobson
Amendola, Boyce, and any other WRs signed will duel for the #3 spot with Amendola having the edge entering camp.
To answer your question I think Amendola was expected to be the starter and excel, his injury and lackluster performance opened the door for Edelman to prove how good he is, he received an offer from the 49ers, which he took back to the Patriots, and they matched. This gives us two slot receivers, but long-term unless Amendola has a breakout season he will be released after the 2014 season.