If you want showoff new generation titles early, buy the new console's exclusives. The games that have only been in development for the next generation. Killzone SF, and Knack on PS4. Ryse and Dead Rising 3 for XOne. I'm holding out on cross-generation games until PS4 and XOne launch, but only because it's just two and three weeks, respectively. Not months. And I'll get some enhanced features and I won't have to swap back and forth between consoles. I'm certainly willing to swap back and forth for titles with no new generation versions. Batman Arkham Origins, for example, back to the PS3. I'd already be playing it but it's my older son's top Christmas wish, so we've already got it but it's hidden away until Christmas. For me, it doesn't make sense to buy last generation versions of games available for current generation hardware when the price is the same and it's available for the new generation. As for buying both next-gen consoles at launch, I preordered back in June. If I had to scramble around all over town hoping I'll trip over the odd unsold launch console, I wouldn't do it. But preordering both was a conscious decision, to get the big hardware purchases long out of the way before there's a new must-have game releasing every other week. I certainly could have waited to play KZ SF and Knack and Ryse and DR3, but I won't have to. I wouldn't have stood in line to play those games soon instead of later but I don't have to wait in line, so I'll enjoy the opportunity to settle in with the new consoles right early.
But, no, besides the questionable merits of bragging rights, and merely for personal enjoyment of something new, there's no good argument for buying the next generation of consoles at launch. Even buying a few months after launch, when most all those launch window games slip to the second quarter 2014 or to the end of the year, there's a lot of dead air playing your previous generation console waiting for something interesting to finally ship for your next-gen systems.
One benefit buying early, you get a whole lot out of games you do have for the next generation. I got untold hours, miniature lifetimes, out of Ridge Racer 7 on PS3.