Keep a sharp eye on that opposite side bearing! Just kidding, the predictive power of a rear bearing failure for opposite side failure is quite low. Most important is that the failure mode of a wheel bearing is one of the nicest of any part on a car. Almost never catastrophic ( unless your ipod is always on high), they whine for a long time (usually weeks to months even w/o lots of highway driving) before they die.
When faced with a whining rear end I would: Remember that everything from the trans output brng to the road surface is officially a suspect, since they all vary with road speed.
1 Check for a dry differential cause its easy and might save me thousands 2 Do the tire thing as you correctly did 3 In the absence of CV joints, dx the wheel bearings. I do not believe the fault can be correctly located by lateral loading (gentle curve or turn) since everything between the wheels becomes loaded or unloaded with side loads with no great consistentcy with regards to resulting noise characteristics. However the FACT THAT IT CHANGES WITH LATERAL LOADS DOES help eliminate tyres as the cause. Tires are suggested by a noise that varies with different road surfaces in a fashion that one can make sense of. Lastly hard machanical noises will increase in pitch and volume pretty much with road speed. Tire noise will more often show a non-linear noise with a "band" of noise say between 55 and low 70s mph the noise peaks, because it is a complicated harmonic of air flow. No one is able to design a tire that is quiet new and quiet thru all of its tread depth Sorry for the long post, best of luck. Tom