There seems to be alot of confusion around level off if you do nothing.
There's a specific requirement for VNAV compatible approaches that it ends with either a RWxx point, or a MDxx point. The first one will have an altitude of rwy height + 50, ie threshold height. The latter is normally the MAP with an altitude which coincides with a typical 3' descent from FAF.
Now to the conclusion, VNAV will always level off at the lowest of either VNAV path hard altitudes or MCP selected. More importantly when MDxx or RWxx is no longer active (overflown), the FMC exits it's approach logic and levels off.
In order to approve an operator for VNAV approaches it has to be established that the procedure will not descend you into the ground. Soooo...it levels off, regardless. Either at MCP selcted MDA, or at MDxx point, or at RWxx threshold. Works a treat.