Here is a related Paul Krugman post. In my view, Obama may propose slowing the rate of benefit increase, but he won't propose an actual cut in Social Security benefits. Use of the word "cuts" is thus likely to prove misleading. I've already argued it is better to cut Medicare than Social Security (in-kind vs. cash), but it shouldn't come as a shock if reindexing benefits is part of a bipartisan budget deal. It's an easier policy "to do" than fixing Medicare, though again I prefer the latter.
It's a common argument that we need not cut benefits now, simply to prevent benefit cuts in the future. The reality is that the long-term budget (don't look at SS alone) is way out of whack, and reindexing now is one way to get larger spending cuts in the future than could be done on a one-time basis. Unless you do reindexing of something, at some point in time, it is very very hard to institute large spending cuts on a dime.
Reindexing is one signal of a longer-term political time horizon.