Was reading that they'll be opening the remaining stations by the end of this year, and that from one end to the other on the light-green Sukhumvit line will be about 1.5 hours. They will also be adding around a dozen new trains to make up for the extra stations IIRC.
Would be good to get the airport 'link' finally linking the two airports at some point, or at least having some metro line going to DMK. The original ambitious metro-plan with 13 different lines still looks a long ways away..