There is a possibility though.
When you import a .MAP file in Hammer 4, I think you can save it to .MAP
It wont save it as a .VMF unless you specify so. The problem is that Hammer 3.4 probably wouldnt open that .MAP file... I'll have to test it.
The "export to DXF" option is useful for Autocad and specially for importing maps into Bryce. But these programs dont have the HL textures, and the whole point is being able to walk through the building in real time.