First, let me admit that I'm talking out the side of my head here, as I haven't been to Chopaka in several years, but I do have a fair amount of experience there. I certainly don't like some of what I've been hearing about it over the last season or so, what with sunfish and bass introductions and what not, but I try to hold out admittedly sentimental hope against dispair.
As good as Chopaka can be (at its best I would rank it with the top trout fisheries in the world - seriously), there have always been years worth skipping. As good as it is, it is still a planted system, after all, and it has always run on cycles, about 3-4 years, with the worst years often following the best. (There is precious little spawning available at Chopaka - in low water years none. Trout in lakes only live so long, and those really big beautiful Chopaka bruisers are actually pretty close to the end of the line.) The good news was always that maybe one bad year would be preceded by steadily improving (sometimes great) ones, culminating in one or two spectacular seasons.
Now I don't know, maybe WDFW isn't managing it as closely as they used to, and the cycles have gotten mucked up. It's hard to believe the incredible hatches could go away. There are at least two major mayfly hatches, several caddis including big traveling sedge, who knows how many chironomids including those massive early-season pink ladies, and one of the best damselfly emergences you'll ever see - after a June trip, you'll have adults emerging out of the folds in your tube and waders for a few days, and the adult-damsel fishing in mid to late June can just get scary. And there can be days when it's all happening at once. But who knows? Maybe the grazing that has always gone on up there has gotten way out of hand.
But it's hard to believe that incredibly fertile system could just give it up. Chopaka is no flash in the pan; it's been providing world class flyfishing for decades. So I'm going to continue to hope that the implications of its demise are premature.
That said, there HAVE always been years worth skipping, and I've been there on several of them. Maybe this is one. However, I will say that I've always thought June was better than May up there (sorry if that just adds to your indecision, Mykiss, and if May REALLY stunk, well...). The good news is that there are excellent fall-backs close by, Ell, Aeneus, the excellent if non-flyfishing lakes like Concunully, AND you're not even that far from from the Kamloops lakes in BC.