Publicly announcing the change of email address (before the change itself) might be a good idea so that you can always refer to that post if someone ever asks you about it (for instance, changing email is sometimes associated with account sale or even hacking).
I don't see how can this make it any better as the new owner might as well come here and create the similar thread and then change the email. I mean, if we are being so paranoid.
I had the same problem before and I was also worried that changing the email would make people suspect that the account had changed hands.
I don't think that changing the email address will automatically make people think that account changes hands (at least it shouldn't) but if there are more changes beside that like a drastic change in posting habits/posting quality, that will certainly make people suspicious. Otherwise, I wouldn't worry much about it.