According to Jim Beaver's tweet, he will be returning to Vancouver to resume shooting for Supernatural in about 12 days time. It's interesting that on the same post, it also mentioned that Jensen's directorial debut will be filmed first. Source SpoilerTV.
According to another post on SpoilerTV (here), the episode 6.04 is called A Weekend at Bobby's.
Now... I don't know if it means 6.04 is to be directed by Jensen or are they two separate episodes? Note, episode order may change too (the CW has the habit of changing episode order around).
I guess we'll know more when Comic Con comes. I can imagine this is the one they will show at Comic Con. If so, I think Jensen is highly likely to be at this year's Comic Con. Logical? Just saying..
And guess who is coming back to Supernatural season six? A.D Sk*ne*! OMG!
EW's Ausiello has revealed on his blog that 6.04 will be a Bobby centric episode directed by Jensen. Details here.