Will silverlight be supported longterm so i can use websites like sky go?
As long as it is whitelisted for Blink, one may count on it being whitelisted for Vivaldi. Even if Blink should begin to block it by default at some point (and they haven't yet, after 16 months of blocking most NPAPI plugins), it's not clear to me that Vivaldi should have to respect that block in their own builds of the engine.
I know of government websites that rely on Silverlight. as long as that is the case, it would seem wrong-headed to block it.