Hi.
I did send email to HTC couple of days ago and today they reply to me and wrote like this:
"Thank you for your enquiry about HTC Tattoo. Unfortunately we do not have any information about the update to 2.1 for Tattoo at the moment. Keep you updated on our website for more information. Best regards, Jan R HTC Tech Support
HTC - Mobile Phones, Smartphones, Cell Phones, PDAs Tel: +44 8458900079"
So it seems that Tattoo will not get 2.1 update.