SAP ERP 6.0 includes the SAP ECC Server SAP ECC 6.0. SAP ERP 6.0 is the "highest" release available.
Recently, the enhancement package delivery mechanism has been made available. Enhancement packages are basically used to selectively install new features in the existing SAP ERP 6.0 (including ECC 6.0), and as such they do a partial update of ECC 6.0. At current enhancement package 3 for SAP ERP 6.0 is available.
If you are interested in these enhancements, I recommend you to look into the SAP Service Marketplace service.sap.com/erp-ehp.
now a days trial version is available on SDN
ecc 7.0 for 90 days
just go through link
and click to download option
My answer is little diffrent with others, even this is in the sync with other answers
SAP is providing Enhancement Packages for new functionality till ERP 7.0 for ERP 6.0
EHP3 is already released for the customers
EHP4 will be available in November 2008
You can find more info on this :
Installations and Upgrades
Installations and Upgrades->
SAP Application Components->
SAP ERP ENHANCE PACKAGE ->
SAP ENH PACK 3 FOR SAP ERP 6.0