The only gamble I see with the cancellation and renewal is if Barclay's adds sign up restrictions like many other banks are implementing. There's no guarantee that in 4 years you'll still be eligible for a new sign up bonus. I'm with you, though... I'll take that gamble.
Our family has 3 Aviator Reds that were converted from US Airways cards. So they are each about 3-4 years old. I cancelled one this morning, the one that doesn't have a 10K anniversary perk. The other one that was up for renewal got a waived fee and small 5K spend bonus, so it was kept for another year.
In the past, I've been very pleased with the random spend bonuses, which included utility spend bonuses. The spend xxx for 3 month and get bonus points was a great deal for us, and kept the cards in use. That utility bonus category doesn't show up in any other card in our wallets and we maxed it out every time we had it. Now, the spend bonus is watered down (get 2x points per $1000 x 3 months, plus 5K at the end), and there's no guarantee that you'll get the offer, anyway. Of our 3 cards, only one got that particular bonus, and we missed the first month's spend, so, whatever...
The other issue is that 10K points ain't what it used to be. For years, that was half way to a Europe redemption, or an easy to find domestic one way. Now, domestic saver space is sparse and international 1 ways can be 30, 40, even 70K. They want to get the consumer back to a lifetime of spending (and paying the card renewal fees and hopefully big interest charges) for that dream trip. The game has changed. We're changing with it.