Ewan McGregor lied for a while to cover up the fact that he was going to return to play Obi-Wan again, although he generally made it clear that he was leaving the door open to return to Star Wars someday.
If McGregor could keep his return secret and deliver an epic surprise for fans with the announcement, isn’t it possible that Liam Neeson could be covering for a surprise appearance in Obi-Wan Kenobi?
And The Mandalorian managed to keep Mark Hamill’s return a secret!
As Jimmy Kimmel noted, Neeson is a good enough actor to pull it off.