He's hoping to go out on a high after managing to turn around the big dip of last season, which is something he failed to do at Dortmund. It's smart timing, as now the press and the neutrals will be behind a Liverpool victory, with Guardiola the main vilain and Arteta a level boss.
I wouldn't worry too much about Alonso if he were to go there. It's a very tough job to move to the Premier League and follow a relatively legendary manager, and it'll be a coin flip if he succeeds or fails. Arteta's lucky to still be where he is, and he's had easier conditions.