Expense Ratios have been slashed across existing funds: https://www.fidelity.com/mutual-funds/investing-ideas/index-...
Premium, Investor, and Institutional classes are all being merged into 1 class with lower fees and no minimums: https://www.fidelity.com/bin-public/060_www_fidelity_com/doc...
For people holding existing Fidelity index funds, you just start paying less now without having to do anything.