I think you might be looking at this the wrong way. It shouldn't be about how long the line is going to be, you should be thinking WHY is EVERYONE talking about it. Hundreds of thousands of people can't be wrong can they?
I love Toy Story and I love Buzz Lightyear but this is such a different and fun ride, cools you off as well. The line queue is very cute and it makes the time go by fairly quickly.
Don't go in thinking negatively about it, you want to have fun while on vacation and many of our fellow Dis'ers gave great info.
The best way to see it quickly and NOT wait long is follow the vacationers at rope drop....they basically all will be going in the same direction, its actually quite amazing to watch. You can't run, you walk in a quick pace and then it eventually splits in 2 big lines....families that just go straight for the ride, others go to FP first and then all get in line TOGETHER so that way they can ride it twice BECAUSE 9 times out of 10 they love it.
What I find to be fun was the Green Army men that were shouting orders at us and keeping us in line, cracked me up and actually surprised a few guests.
If you have never tried it, do it at least once.