I wrote a blog post some time ago about using SQL Developer 3.x to connect to SQL Server. I tried the same thing today from SQL Developer 4 EA2 and it works just fine.
You have to download the 3rd party JDBC driver and point SQL Developer to it. You can read how to do it here.
Cheers
Tim…
Update: My colleague just told me this.
“If you at any point decide to use Windows authentication to connect (like I just did), you might hit this error:
Status : Failure -I/O Error: SSO Failed: Native SSPI library not loaded. Check the java.library.path system property.
…found a work around, which involves copying the ‘jtds-1.2\x86 (or X64)\SSO\ntlmauth.dll’ from the JTDS directory to the JDK’s \jdk\jre\bin folder. Then I restarted SQL Developer and it worked J”