Minecraft 1.8 will be released in a matter of days and a leaked copy has already been made available.
World generation has been changed as part of the update therefore seeds will not create the same worlds in 1.8 as they did in 1.7. As a consequence the seeds we have shared prior to today will not work in Minecraft 1.8.
However, 1.8 contains many interesting new terrain features (rivers, ravines, abandoned mines) and in time epic seeds will be discovered. We look forward to sharing the best 1.8 seeds with you very soon!