If you own Lightroom 4, and have a valid serial number, yes you can switch.
Are you using Mac or Windows Computer?
Which Nikon Camera are you trying to tether in Lightroom?
Refer A list of cameras that can be tethered to Lightroom. and your camera is supported.
I believe the OP is using a Mac with El Capitan and tethering is broken due to Apple removing functions from the latest OS that tethering relies on, so I think the OP is effectively asking if LR 4 supports tethering Nikon on El Capitan.
The answers about LR 4 needing a valid serial number and what cameras LR 4 works with are secondary to this assumed primary question. I don't know the answer, but the OP could download LR 4 and run it as a trial w/o a serial number or use their serial number to license it and see if it works and tell us if it works.
Various versions of LR installers are available, here: