While I love all these stories of turning your friends and loved ones into chat bots so you can talk to them forever, my brain immediately took a much darker turn because of course it did. How many emails, text messages, hangouts/gchat messages, etc, does Google have of you right now? And as part of their agreement, they can do pretty much whatever they like with those, can't they? Could Google, or any other company…
Even if Google's privacy policy permitted such a tectonic shift in data use, integrating Gmail data into Bard would involve opt-in consent from you AND your email correspondents (an infinitely difficult task). Peoples' expectations of privacy in email are very, very high. So even though you have a copy of everything your friends email you, they would need to all be involved in your agreement for this change of data use.