I'm a Pathfinder charter subscriber and I'll continue to support Paizo. In fact, this announcement has me excited to test drive the alpha rules and bump up the priority for my running of Rise of the Runelords and the other paths. I've had Paizo's stuff in a holding pattern for my homebrews because we're running in DCC World (Aereth) at the moment, but I really think this announcement will be good for the industry, and it definitely lessens the sting of my 3.5 books' obsolescence (without a published line of adventures, I'd be "all homebrew prep, all the time" in a few years).
All my players have expressed interest in Golarion (and only passing interest in 4E), so I have no doubt that the seats at my table will be full for a long time to come! I think 4E will succeed, and I still intend to support it as an RPGA DM, but this announcement has given me hope that 3.5/OGL will continue to hold mindshare out in the gaming world rather than becoming just another artifact of the past. Since I am rather heavily invested in 3.5 books and minis, that makes me happy.
Good on ya, Paizo. I hope you succeed beyond your expectations, and you've got my support.