Can we please stop with these completely incorrect statements about Whistler's snow during the Olympics? Whistler had an amazing winter during the Olympics. Cypress, located in Vancouver and host of the bump events among others, had a poor winter. You aren't the first person to conflate the two, but it's really aggravating--especially since conditions at Whistler and the Vancouver hills are totally different.
For the OP: Whistler in early April can be quite good, particularly if you stay at the top third of the mountain (the top 1800' or so). It was great this past year. Like others have said, weather patterns are anyone's guess this far out; best to hold off booking anything until we see what the forecast looks like.
They had to cancel several of the Alpine event training sessions and move a couple of the early events because it was raining. At Whistler, not Cypress. (Of course, then they had to cancel some more because it was snowing and visibility was bad.)
...On the eve of the first race, Saturday’s men’s downhill, successive days of fog, rain and sticky soft snow prompted the cancellation of training runs and raised the prospect, or even the likelihood, that the event would be postponed one or two days. Racers weighed tactical or ski wax changes with an eye on a forecast for unsettled weather until Sunday. It rained most of Friday morning and into the afternoon, turning the snow on the race course soft and sometimes slushy. The lowest temperature overnight Friday and through Saturday was expected to be 36 degrees.
“I think we all knew this could happen; at least anyone who has been here before knew it,” the veteran American downhill skier Marco Sullivan said. “It’s not exactly a surprise. The downhill will go off eventually, and the best skier that day will still win.”
They do get a LOT of snow. And they actually had a huge year overall in 2010. But they're too close to the coast to have winter-like conditions in the spring.