when the Etna was scrapped, the guys over at HoFo said that the Targa was originally designed to be a follow up/upgrade to the Bionic/Etna. so, it was going to probly be the Bionic2. but then the Etna got scrapped, and they just assigned the Bionic name to the Targa.
so, it is a completely different device than the Etna. but, as we have seen in recent history with the Inc2, DX2, D3, etc, it was only going to have incremental upgrades - the processor change, webtop, and ram. so, it's a different device, with some upgrades - and the debate here is mainly a subjective one as to whether those upgrades can be considered "significant."