Just look at Virgin Blue in Australia, going strong for 5 years...
Yes - but ZA already has two (or is it three) LCCs?
Branson is not one to buy existing companies - he prefers to start things from scratch. When the market is already full it would be a strange decision to try and get in via a carrier that is not geared for LCC. I don't think this will happen.
If Virgin
does want to work with Link, it will be to arrange onward passage of their long hauls and many of those will be Premium Economy and Upper Class pax, not LCC material. VS used to have a deal with Nationwide but they are now competition (sort of) on the long haul.