1) How many times have HasTak released accessory sets for Transformers? The probability of HasTak releasing an upgrade kit for Classics Ultra Magnus is essentially zero - with or without fan kits. The 3rd party kit just wont affect HasTak's bottom line. The probability of a Sunstreaker reissue drops significantly with the fake on the market. Before it might have been something they were looking at - but now it wouldn't be anywhere near as likely.
2) How many consumers buy a second version of a Transformer with a hat? Sure many fans do, but not all - because of the expense. And I'm betting fewer kids would but the same toy again - many parents won't buy the same toy twice if they can help it.
3) I doubt that the kids would buy the 3rd party upgrade kit in significant numbers, whereas more might buy the KO in the market stall. The KOs have a much wider reach.
Then there's this...
The fact remains that 3rd party accessories are just that. They're not marketed as genuine, nor are they trying to dupe anyone into thinking that they are. The recent KOs are released in packaging that is trying to trick the unaware into thinking it's a HasTak product. Granted, many will be looking on the secondary market, but the flood of KO Sunstreakers on the market now means less chance of income for HasTak if they release an Encore Sunstreaker next year. Some will make the informed decision to buy the third party product, many wont. Many who make the decision not to buy fakes could well end up with them unwittingly.