Growing up and going to college, no less. Definite parallels.
Also take into consideration that TBLT has a different, arguably happier ending than the book it's based on. IIRC, in the book, they end up with a new, completely different family rather than being reunited with the Master. Does that make it more or less likely that TS3 will end up with Andy bringing the toys with him? You decide.
And yes, a crossover would be pretty fricking sweet. I wish there weren't already sequels to it so Pixar could just do TBLT2, rather than having to do a 4 or an unnumbered one with a subtitle (the numbers are confusing anyway, since the second sequel is an interquel) or a continuity reboot. Although they're really not that bad for direct-to-video fare.