You're also correct that this is an implicit admission of guilt. It may be enough to mollify the Congress, in which case, the "probe" will go no further.
Sacrifice made and accepted.
I wouldn't be so sure. A scandal can be very valuable politically and we're not all that far away from the 2012 election. Both Grassley and Issa are Republicans and, even if the "probe" ultimately leads to a dead end, the attention that it draws could be very politically damaging to the administration and, by extension, the Democratic party. Keeping this whole thing simmering for the next year and a half and ramping things up close to the election could be a very viable strategy to take the White House.
What I see happening here is throwing people lower on the totem pole under the bus in hopes of tying the whole thing off before it gets too high. An indictment or two, however, could probably counter that because people seem to be much less willing to "take one for the team" when prison time is involved. I think obstruction of justice could probably work nicely here.