Personally, I would discount the occurrence of a nova event--or any other such catastrophe--at any time in the foreseeable future. That would be based on two primary lines of evidence.

First, you can't really find what I would consider reliable evidence that They are making any preparations for the survival of any large number of people, even a few hundred thousand. You can any number of narratives about underground civilizations and bunker cities for the elites under mountains, etc, etc, but none of these ever seem to interlock with one another as you would expect to see with fragmentary revelations of an underlying truth.

Second, why would they bother with depopulation programs a century old if all us poor surface dwellers are just going to get boiled and suntanned to death? I suppose one could say it's just misdirection to throw us off the huge secret, but then again there's no independent evidence of there being a huge secret like that.

None of this means catastrophes haven't taken place before. It's pretty clear to me that a comet struck 13,000 years ago, kicking off the Younger Dryas and creating the Great Flood, among other things. The mainstream derides this as "conspiracy theory", yet promotes all other manner of disasters to frighten us. Puzzling.