Do proponents of Federal Vision believe that there is no hope of salvation without baptism? According to my reading of this article written by an opponent of Federal Vision, physical water baptism is required for salvation according to those who advocate the framework:


  Some would insist in all this that they do not deny the doctrine of justification by faith alone, but say that faith and salvation are both conferred through the sacrament of baptism. What this does, of course, is to make everyone in the church a believer, whether or not he really is a believer, and it also gets rid of the need for conversion since everybody is a Christian from the moment the water of baptism is sprinkled upon him.  


(my emphasis)

Is this an accurate characterization of this theology or is it a caricature?
&quot;That depends.&quot; Most FVers define salvation as &quot;the state of being joined to Christ through membership in the Church.&quot; If baptism is the event that initiates this, then baptism is the means of salvation defined in this way.
From the Federal Vision Joint Statement:

We affirm that membership in the one true Christian Church is visible and objective, and is the possession of everyone who has been baptized in the Triune name and who has not been excommunicated by a lawful disciplinary action of the Church.
We deny that baptism automatically guarantees that the baptized will share in the eschatological Church.

So no, I don't think this is an accurate characterization, at least based on official FV statements that I've heard. Lots of disagreement seems to come up because both sides work from different sets of terms.
Also, there can be many abnormal circumstances, such as the thief on the cross, where baptism is not possible.