Not a chance. No LG mobile handset has ever been—nor likely ever will be—supported by iSync, unless the Palm OS license signed earlier this year results in the manufacture of Palm OS-based smartphones by LG.
The only mobile handsets supported explicitly by iSync are listed here:
http://www.apple.com/macosx/features/isync/devices.html
Cross that with the list of available handsets and smartphones available from Sprint, and you will find almost no common devices. No Nextel iDEN handsets are supported at all. Blackberry and Windows mobile devices require additional third party software, and the Palm Treo 700p works far better with the Missing Sync for Palm OS than it does with iSync.
As a matter of fact, I'll save you some time, and simply state that the Palm Treo 700p is the
only device currently available from Sprint/Nextel that is explicitly supported by iSync. Sadly, it's that simple.