The major reforms to Senate Rule XXII sought by progressives are not to be. Instead the likeliest reforms to occur on this as soon as today will be along the lines of the Levin-McCain proposal. The odds favor this bipartisan reform package and thus should be done with the 67 votes required by Senate Rule V (but not the Constitution). Majority Leader Harry Reid (D-NV) is unlikely to use the Constitutional Option (or Nuclear Option of passing a rule change with less than 67 votes, but with more than a majority).
The significance of this is that the Senate should be less burdened by minority obstruction of procedure. This is a good sign for future negotiations around debt ceiling, sequester and a budget, as well as Senate legislation generally.
Expect reforms to: limit debate on the motion to proceed (the easiest path to obstruction); allow minority amendments (the minority being able to offer amendments, or alternatively the majority being unable to fill the amendment tree in some instances), a reduction in post-cloture debate; and a streamlining of the conference process (collapsing motions to insist, request and appoint into one non-divisible motion).
All that said, these reforms are window dressing as they will be enacted as a Standing Order that expires at the end of the 113th Senate. As important to realize, so one does not become giddy at the prospect of legislative momentum in the Senate, is that all of these reforms are at the prerogative of the Senate Majority Leader and does not in reality change the status quo. Pragmatically Sen. Reid will be reluctant to allow Minority Leader Mitch McConnell (R-KY) to offer amendments, which in turn allows the Motion to Proceed to be debatable (and thus filibuster-able).
This is a very good sign in respect to the comity of the Senate and could lead to constructive deliberation. Yet there remains immense potential that the Senate falls back into the obstructionist traits that have defined it the last four years.