The line of succession after Georgi Michailovich is disputed.
One possibility is that it passes to the descendants of Maria Vladimirovna's aunt, Grand Duchess Maria Kirillovna, who was married to the Fürst zu Leiningen; namely the claim would pass to Andreas, Fürst zu Leiningen, and after him to his son Ferdinand. But both them aren't Orthodox, and in addition the marriage of Maria Kirillovna to the Prince of Leiningen could be regarded as morganatic.
Another claimant is the brother of Fürst Andreas, Prince Karl Emich zu Leiningen, who in 2013 has converted to the Orthodox faith and proclaimed himself Tsar Nicholas III.
Then there is the claim of Prince Dimitri Romanovich.
The whole (messy) issue is better and lenghty explained in these threads: