I've compiled a list in my head for the points for Syed having slept with Danny and against!
For:
1. Syed has been written out of character recently, so this would just be one step further. It also seems like one of BK's plots.

2. We don't know what happened after the kiss.

3. Johny's interview and mag write ups certainly seem to imply that Syed did sleep with Danny.
Against:
1. Surely EE wouldn't bring Chryed down that low! (or would they?!) And didn't BK say in an interview once that Chryed would never cheat on each other - I mean I get the kiss is cheating, but I think BK meant cheating in the more biblical sense.
2. During the wedding episode, Syed was the one who insisted that it wasn't just a kiss, it was even worse than that in his heart. Why would Syed say that if it really was more than a kiss? It seems pointless. And Marc's acting during the moment made Syed seem almost sickened at the thought that he had actually slept with Danny.
3. There was a spoiler that said that after Syed rejects Danny's advances, Danny tells a terrible lie. Basically, Danny's a lying jerk.

4. Masood saw Syed kiss Danny - and wouldn't Massod tail Syed afterwards to see where he was going? Masood seems convinced that it was just a kiss, so maybe it was!

5. The fact that Christian believes that Syed slept with Danny, when Syed didn't seems like added drama that EE would love.
6. Actors like to tease viewers so interviews are highly misleading, and so are spoilers!
7. Syed loves Christian and would never have slept with Danny, then lied about it to Christian. :sleep:
Lol, so this is just my list! Hope it's somewhat helpful to others, but basically the fact that the points against Syed having slept with Danny outweighing the points for is the only thing that's keeping me from punching things!