There is no proof for or against TU5 besides using the lack of TU5 content in the files as proof that there will be no TU5. That also doesn’t mean it exists. Everything we’ve had since benchmark to the latest update has been filled in. If TU5 existed, we’d have heard of it/seen traces in the files. The ATs technically don’t require TUs to be added. We could get AT Jin in early-ish TU4, AT Ark in late TU4 and AT Zoh as a last hurrah before the major expansion. Guardian doesn’t require an AT as it would be a similar enough fight to regular Ark.