The more imminent concern is that publishers are beginning to bundle browser runtimes completely replacing native browser functionality along with its established privacy and fair use expectations. Say hello to unskippable interstitials, unblockable analytics and targeted advertising, content that can't be linked, saved/archived, mirrored, cached, shared, translated or made otherwise accessible.
Developers mostly discuss JavaScript shortcomings and new possibilities offered by WebAss, but seem otherwise happy to completely throw the fundamental architecture of the web under the bus.
Technically, what WebAss can do has since long been possible with native applications; the only thing added here are new software licensing models, eg. pay-per-use, but mostly tracking/ad-financed.