Vela enjoyed his best season thus far, scoring 16 league goals as Sociedad finished seventh in La Liga last term, leading to reports he may leave the team.
His form has not gone unnoticed with the striker being linked to former club Arsenal, who inserted a €4 million buy-back clause when the player departed for Sociedad in 2012.
But Arrasate remains "optimistic" that the 25-year-old will choose to stay at Anoeta next season.
He told AS: "I know how Carlos Vela is and I understand that he's happy here and if that's the case, there's always a chance he'll stay. I'm feeling optimistic."
Sociedad team-mate Griezmann is also being linked with a move away from Spain, with the Premier League the most likely destination.
Arsenal are again among the suitors following the France international's stellar campaign, which resulted in 21 goals in 50 appearances in 2013-14.
The 23-year-old, who is set to appear at the FIFA World Cup in Brazil, is likely to continue with Sociedad next season according to Arrasate.
"Right now, he's only focused on the World Cup, but as I understand it, he will continue," said the 36-year-old.
"He's a player who has a contract with us, so he will need to join us."
Arrasate added: "It's not easy to pay €30 million for a player and that makes us relatively calm."
