[CentOS] Outdated packages on 5.1

Hi,

A package verification on recently CentOS 5.1 reveals that some packages 
is outdated comparing with the 5.0. Here are some examples:

5.0                                   5.1

tzdata-2007h-1.el5            tzdata-2007d-1.el5
libpng-1.2.10-7.1.el5_0.1   libpng-1.2.10-7.0.2           
perl-5.8.8-10.el5_0.2         perl-5.8.8-10

The "updates" directory on CentOS 5.1 repository does not contain the 
latest versions of some packages available for 5.0.

Any reason for this or should I just wait for the release of these updates?

Regards,

Heitor A. M. Cardozo