It'll be supported once CoreLibs lands in AG for Mac. CoreLibs is the new cross-platform engine for AG, which will be used for AG for Windows, Mac and Android (instead of using separate engines for each platform). There's really no ETA for landing and releasing this, as they're focusing on landing it for Android first (parts have already landed), then Mac and then Windows. It's not going to be a simple or quick process either and will need to be heavily tested because in all likelihood there will be bugs. But as far as I know, CoreLibs already supports HTTP/2 so once it lands it'll gain support.