Great help! Thank you very much for your great post.I found this in the Eris section of this forum.
HTC says Hero and DROID ERIS will receive Android 2.1 update, new Sense UI
Official HTC Hero Android 2.1 ROM Update Coming In April 2010
Hope it helps. If you want more info there are a bunch of threads there to peruse.
I have read that if you root your Eris then you can manually install the leaked version that came out not too long ago, but since I don't own one, I haven't put much research into it.