I have one relay on CentOS 6 and one on CentOS 7. The one running CentOS 7 hasn't had the 0.2.8.8 update yet and so is still running 0.2.8.7. The one running CentOS 6 has had the latest update.
by "latest update" you mean 0.2.8.9?
Where do you get your tor packages from?
If you got tor v0.2.8.9 on CentOS 6 before 2016-10-22 20:50:29 (UTC) than your package source is not epel(-testing).
Is there a problem with getting CentOS 7 packages out?
How much of a problem is this? Both now and in the future?
It usually takes about a week to get a new release into the epel-testing repo and another 2 weeks for the epel (stable) repo.
If you want to get the current latest tor release (0.2.8.9) now you can temporarily enable the epel-testing repo - if you don't want to enable it generally:
yum install --enablerepo=epel-testing tor
https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2016-2f6f1435ed https://bodhi.fedoraproject.org/updates/FEDORA-EPEL-2016-f0f6483aa7