installing drop in tub

is it possible to use Wilsonart HD laminate for around the top of a drop in tub unit?

If the laminate is used on top of plywood and the drop in tub is going to sit on it and you seal the tub/laminate contact area with caulk it should be fine. Use a good quality caulk.

Be sure to check the laminate manufacturer's spec requirements. Many laminate manufacturers will not honor the warranty if it is not installed over a "voidless" substrate, i.e.; particle board or MDF (medium density fiberboard). These materials are not really ideal for high moisture areas.