Fannie 3.0s and 3.5s (and anything else for that matter) just haven't lost enough ground to cause any serious concern about negative reprices.  They've been handily outperforming Treasuries as well, but therein lies the problem.

Treasuries have been consistently weaker, and there's only so much of that that MBS will be willing to tolerate before acquiescing to the weaker bias and ultimately losing enough ground for lenders to be considering reprices.

As such, now's a good time to get ready to pull the trigger if it's something you might have done in the event of a more forceful reprice alert.  If your lender has a history of giving any weight to Treasury movements (very few do, but it does happen from time to time), we've already seen enough weakness for some exceptionally small level of concern.  In general though, it will take a bit more weakness--especially in MBS--to raise the chances of actual reprices.