I'm not sure how acceptable this is for CPAN, but you could write a thin wrapper for your Business::TPGPost module called Business::TNTPost. You would then keep the original module updated under the original name, but new users could still find and use the new one via the new name (with Business::TPGPost being a dependancy).
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It's all fine and dandy until someone has to look at the code.
I would actually recommend doing the inverse. Write the new Business::TNTPost (or whatever name you most like, company agnositc is best to avoid this same issue in the future), and then re-write Business::TPGPost to be a wrapper around it.
My reasoning is that the TNTPost is the new name, and so is the "future" of this module. While the TPG is the "past" and should eventually be deprecated.