Based on what I can see, value has accrued to the fetchlands instead of the mythic rares. This tends to happen when there are high value rares in the set. Comparing Dragons of Tarkir and Magic Origins is a great comparison to show this effect. DTK has a few pricey rares which have soaked up a bunch of value, while ORI does not and the mythic rares are the most expensive cards in that set.

The outlook for KTK is positive at the moment; there has been lots of activity in paper on the Frontier format. KTK has many staples of that format. Although Frontier is not a supported format on MTGO, redemption is kicking as demand in paper increases.

The big caveat is the redemption window is closing. KTK is past the guarantee date but not the cutoff date. We’ve already seen KTK sets briefly go out of stock in the store, and this tanked the prices of all cards in the set.

Your challenge will be to balance the risk of redemption ending with the potential for some gains. I would lean towards selling sooner rather than later.