You will definitely be able to max everything. Annoyingly, Oblivion doesn't let you use anti-aliasing with bloom turned on, so if you want the best of both worlds, you can enable AA outside the game using your gpu's drivers.
However, if you plan on modding the game significantly, it'll be a different story. There are graphical mods that make the game just as impressive as 2010 releases. Unfortunately Oblivion's version of the Gamebryo engine is very poorly optimized for multi-core processors, and a heavy load of graphics and AI altering mods can challenge any cpu currently on the market. The results are definitely worth the effort though!