I've been out of the game for a few cycles. I have a couple friends in the same boat. 3 out of 4 of us that I've talked to about it are curious to start back up with the rotation and the new core set.
Obviously it's a pretty small sample size I'm working with, but that has been our knee-jerk reaction. Rotation alone? Whatever, there's a handful of really impactful cards in the first two cycles, but nothing that will fundamentally change the game. But the new core? We're now looking at rotating out Kate, Noise, Core HB, Desperado, Account Siphon, Corroder, Yog, SanSan, Astroscript, Breaking News, Scorched Earth, and Accelerated Beta Test. Some others, too, but those are most of the impactful ones. And just... wow. I have a hard time imagining what that metagame will look like, but I can't wait to find out. This is like getting a fresh new game, and I have to admit to being really interested.
I think the new core set was the best decision they've made in a long time. If my (again, limited sample size) experience is any indication, it will start to grab some old players back into the game. And with excitement buzzing about a new entry point to the game, new players might start to pay attention too. At this point, you can be super transparent when getting a new player into the game what they should buy... start with a core, figure out what factions you like, buy the boxes with those factions in them. Then as you discover cards you like but don't own, you can buy the packs with those cards. No need to go full-on investment into owning everything, or even everything that's tournament-legal... just the stuff you want.