The OP is asking about Virgin America, a U.S. domestic airline based in Burlingame, California.
Delta did not buy 49% of Virgin America. Delta bought 49% of
Virgin Atlantic, which is an international airline based in Crawley, United Kingdom.
The two airlines were both started by entrepreneur Sir Richard Branson, and both have aircraft painted with a same logo on the tail. However, they are entirely different companies. (There's also Virgin Blue in Australia.)
Fast-growing Virgin America is not a profitable airline (although it reported an operating profit for the most recent reported quarter, the third quarter of 2012).
However, there have been no reports in the business press about Virgin America "going out of business possibly in April." I don't know where the OP heard such a rumor. The only reports have been that Virgin America is slowing its rapid growth somewhat, including slowing down the delivery of new aircraft.
With the U.S. legacy carriers consolidating down to just three, there are opportunities for new airlines, especially ones like Virgin America that provide a superior product.
That said, there's no telling what the status of Virgin America will be in five years (thriving? defunct? just hanging on? merged into a another airline such as JetBlue?). But I absolutely would not worry about tickets for June 2013.