I love the Syrio-Jaqen idea, but I'm unsure of it. I often thought it suspicious that Syrio was killed offscreen - all we have is Arya running away and then seconds later hearing someone screaming as they are butchered. It is Meryn Trant who Syrio faces, and Meryn does not appear to be injured or in any way unsuccessful in dealing with Forel - and if he'd failed to kill the First Sword of Braavos, as well as failed to stop him escaping, I'm sure we'd see some evidence of it. But there is nothing from Meryn after the deed.
It's possible Syrio played dead and Meryn was satisfied that he was, and as pointed out it makes sense for Jaqen to be travelling north at the same time. However, the screams seemed real enough and plenty of people would be fleeing the capital at the time, whether freed or captured.
So... who knows. It would be awesome if he survived to become Jaqen, though. Both characters are awesomesauce.