Short term you'd probably be crazy to sell now prior to ATC coming back with (presumably) positive news from the conference.
That said, this Cache coin stuff at first blush is... not great. Anything that dilutes features, investor interest, etc. away from XC and into another coin, particularly one with essentially zero market cap prior to today (no offense to dev) is negative.
What would be fine is if XC has features that allow other coins to integrate into it, but DO NOT encourage investors to invest in those other coins.
That is not how it would function, and all great feats take a while to accomplish. While people may not ride the train on an alt that is doing something innovative and the market cap is low, it does not make the achievements pushed out by the dev any less. I am sure no one will complain when its completed, it will solve 90% of crypto's adoption issues across businesses websites/point of sale systems. Most of the issues that people have with adopting crypto has to do with bugs in the code causing issues. Shoot, even in the new btc protocol there is a huge bug that would enable theft of an exchanges entire balance. These types of things cannot be ignored for months like is being done currently, so we are addressing the issue.
This is about innovation and adoption. If you demand that there be "One coin to rule them all." Then you may as well be saying what the btc promoters are saying: "Alt coins are unnecessary, bitcoin has everything we need already."