@John ******
well I'm not saying you're guaranteed to get a Visa... I just said if you actually get a new Visa approved any previous visas are typically void.
If you apply for a new visa and you don't get it your old Visa is not void unless you ask them to void it typically.
The generic rule is that you can't hold two Visas for one country at the same time at least in general.
I've heard of people who have gotten DTV Visa while having a retirement extension with re-entry permit, if they sctually get to the TV Visa, their extension is canceled.
But I think for work visa or student visa you may explicitly need to cancel them in many cases...