[CentOS] about major version upgrades

Hi all,

In http://goo.gl/Krjfh I read:

+++++++++++++++++++++++ Upgrading from CentOS-4 or CentOS-5: We recommend everyone run through a reinstall rather than attempt an inplace upgrade from CentOS-4 or CentOS-5 +++++++++++++++++++++++

Do you ever now if that advice will be up to date for the 6 to 7 upgrade?

What is the preferred upgrade process if some want to upgrade inplace? I mostly run virtual guest in a one-VM-per-service (MySQL, php, Mail, DNS, NFS/SMB) basis, with a main + spare physical machine.

I'm installing 6.2 on our dev servers and try to pre-evaluate the amount of work when 7 will be released.