Can reprepro accept a new version of a package into the repository?
Reprepro is not able to hold two versions of a package in the same distribution.
See answer to question 3.1 here: https://web.archive.org/web/20120103201823/http://anonscm.debian.org/gitweb/?p=mirrorer/reprepro.git;a=blob_plain;f=docs/FAQ;hb=HEAD
When you build your dpkg, you should increment the package version as per here.
The Debian Revision Number (the -xxx at the end of packages) is the one you should increment.