I think that the renegotiation was a smart move for both of them. It sends a message that the marriage is important to him and it gives her a greater incentive to stick around and let him prove himself.Hopefully they will be able to make their marriage work and Tiger will be a changed man from here on out.
Either way I think Elin was smart to renegotiate, that way she will have a little something for her future if it doesn't.