From this sample on msdn, I would said that dispose is still required.
using (SPSite oSiteCollection = new SPSite("http://Site_Name"))
SPWeb oWebsite = oSiteCollection.AllWebs["DeleteWebSite"];
I also had a check at the source for the Delete method. All I see is a call to SPRequest.Delete(string) by passing an url, so I really don't see any (simple) way it could perform automatical dispose. That said, it is possible that the deletion performed by the SPRequest class fires some event that in turn disposes all the "active" SPWeb istances (SharePoint seems to keep track of all of them internally), but... to quote the Guide... its just highly improbable.
I have had a look to the implementation of the Delete method on both SP 2010 and 2007. It would seem that the main difference is the addition of the recycle flag to the SPRequest call. This would point to the SPWeb istance not begin disposed: think about it, you delete a web by sending it to the recycle bin and the istance is disposed? won't make much sense IMHO.
Had also done a little test: deleted a web site and then called dispose. The log DIDN'T show the usual "Detected usage of previously closed ecc ecc" so we should be clear. The SPRequest method also doesn't seem to perform any of the operation performed by the SPWeb.Close() method (which is internally called by .Dispose).
As last evidence, I would also point that to my knowledge, the SharePoint Do NOT Dispose guidance doesn't include any reference to the web delete method, so we can safely assume that the istance is NOT disposed.