I'd expect some upward pressure on price because the ETFs will own bitcoin.
But to your larger, exaggerated ("everyone"), question: It'll make it easier to include bitcoin as a part of larger trades when it can be bought and sold and used as collateral like a regular stock. It'll be another tool used by professional traders. I don't think it'll be a world-changing event, and like you said, it's probably not going to increase aggregate demand as trading desks will shift out of complicated ownership structures to use the ETF instead.
But to your larger, exaggerated ("everyone"), question: It'll make it easier to include bitcoin as a part of larger trades when it can be bought and sold and used as collateral like a regular stock. It'll be another tool used by professional traders. I don't think it'll be a world-changing event, and like you said, it's probably not going to increase aggregate demand as trading desks will shift out of complicated ownership structures to use the ETF instead.