I agree with this 100%. The signs are already there. Take the 2013 and 2014 sets as prime examples.
The Republic Gunship, AT-TE, and have blown away many similar OT released sets. The Republic Gunship currently sells for around 300 while you might get 150 for Jabbas Sail Barge. Both were released the same year, and both retired at the same time. The AT-TE sits around 200. Jedi interceptor is now around 70.00 when you could pick it up for around 20 in early 2015. Meanwhile the A-wing is about 50.00. In 2014, it's evident now I should have spent more time accumulating MTTs instead of Cantinas. That sets rise has blown away sets like the Cantina, B-wing, and all the Jabba released sets from the OT era. Just recently Obi's interceptor is outpacing the Hoth Attack and droid escape by quite a bit, and they all retired at the same time and cost the same amount. While the AT-AT and ISD have done well and seen great gains, those are just two sets out of many. In 2015, recently retired exclusives like the Battle Droid Carrier, and Hailfire droid are already rising quickly, much quicker than the OT sets, although the Jedi Duel is showing promising signs.
In the AFOL world, I think older gen-xers that grew up with the original Star Wars films are now a market that is decreasing in size, while the milennials are a growing market. Seems fairly evident to me.