From the base OS perspective, the limit has gone.
With Vista pre-sp2 it depended on the version. See http://stackoverflow.com/questions/413110/which-is-the-maximum-number-of-windows-concurrent-tcp-ip-connections/929973#929973
Since Vista SP2 the limitation have been removed from TCPIP.SYS, and has been configurable through a registry key. Windows7 should follow that same behavior (source and for 7, and here), but of course we will not know for 7 definitely until RTM since appart from technial there may be license restrictions.
However, IIS introduces its own limitations, depending on the version of the OS. For Windows 7 this limit is between 3 (Home Premium) and 10 (Business, Enterprise & Ultimate) simultaneous connections . Depending on your scenario, it might help to lower the connection timeout to free up slots sooner.