I am as well interested in this.
I just launched a new instance and discovered is not coming with 7.4
Since you mention that you already submitted the packages... do you think it's a matter of days before they are available?
I understand it's out of your hands and depends on AWS processing. But if you could give me an estimate from previous releases, from the time you submit to when they are available, it would be great.
Would be a pain to make all the process of starting a new instance, configuring varnish, ssl, adding the content of htaccess files, migrating content and making sure everything works, troubleshooting, etc... just to have 7.4 available a couple days later.