No, the vB5 version is entirely separate as it's a re-code almost from scratch due to the significant differences between vB4 and vB5.
It's possible to replace your vB4 license with a vB5 license for 25% of the cost of a new license, or upgrade to a Dual vB4/vB5 license for 50% of the cost of a new license. This is done via the [Renew / Upgrade Licence] link in the Client Area.