In this weeks Best Buy ad they are advertising preorders for Star Wars The Last Jedi on 4K Ultra HD and Blu-ray already. The home release date still has yet to be announced though. Best Buy will offer these movies in Exclusive SteelBook editions as well.
• Star Wars: The Last Jedi SteelBook Blu-ray / DVD - $29.99 (Best Buy Exclusive)
• Star Wars: The Last Jedi SteelBook 4K Ultra HD / Blu-ray $34.99 (Best Buy Exclusive)
• Star Wars: The Last Jedi Blu-ray / DVD - $24.99
• Star Wars: The Last Jedi 4K Ultra HD / Blu-ray $29.99
So far tonight I have only seen preorders up at Best Buy, but others retailers may start as well. Here is the direct link to the preorders page on BestBuy.com.