The team of modders working on a popular trailer in 2016, up until now.
One of the interesting details is that they're not aiming for a one-to-one recreation of Oblivion, saying that, "its generated world left a lot to be desired" and that they're making changes in the landscape "using pre-established lore, and a bit of creative licence." That includes more plants and other assets in each area than Oblivion's version of the Creation Engine was capable of.
The UI is also being changed, as they "needed something soft, elegant, and not as dark and Nordic as Skyrim's UI" and Oblivion's UI was no looker either. Some of Oblivion's mechanics are being preserved, like spellcrafting, quick-casting, and underwater combat. Personally I wouldn't mind if they skipped item repair, but spellcraft was always fun.
Also of note, while the original score will remain, two composers working with the team are adding to it. As they point out, Oblivion had only 26 minutes of exploration music—over an hour less than Skyrim. Frankly, I turn the music off in Elder Scrolls games after a while and play my own, both to avoid the repetition and because sudden combat music is jarring, but I'll certainly listen to the new stuff once or twice.
You can find out more at Morroblivion is fully playable and contains all of Morrowind's quests.
