This link reports that Issa has said 31 House Democrats will vote to cite Holder for contempt. From that link, I am taking it that Issa feels confident on how next week's Committee vote on the contempt citation is going to go:
Here is a link to a 2007 Report from the Congressional Research Service on the history and legality of Contempt of Congress citations: http://www.fas.org/sgp/crs/misc/RL34097.pdf
Apparently, the House has the power to send the House Sergeant-at-Arms to arrest Holder and imprison him in the Capitol jail for the remainder of that session if they choose to invoke it.
It appears the Committee vote for contempt will take place
this Wednesday, June 13
June 20th. However, the Committee can vote and then choose not to send it to the floor, so no idea when the full vote on contempt will occur. I do know that Eric Cantor has sent a letter to the Department of Justice giving them a June 20th deadline to comply, so I would guess that is when the House will vote on it should DOJ not comply.