Jebus. Leave it to the Mac Rumors community to argue over 2 totally correct answers because they never bothered to define the question first. Let's try finding both.
1) Is the number of jailbreakers significant enough that jailbreaking is here to stay and will continue to thrive?
Yes. It's significant to the jailbreaking community.
2) Is the percentage of phones that are jailbroken high enough that it will drive Apple to make major changes to attract and hold on to that demographic in the future?
No, they would probably sell more phones to new customers by making a pink iPhone than they would by shipping the phones with Cydia pre-installed. It's not significant to Apple's sales numbers.
1) Is the number of jailbreakers significant enough that jailbreaking is here to stay and will continue to thrive?
Yes. It's significant to the jailbreaking community.
2) Is the percentage of phones that are jailbroken high enough that it will drive Apple to make major changes to attract and hold on to that demographic in the future?
No, they would probably sell more phones to new customers by making a pink iPhone than they would by shipping the phones with Cydia pre-installed. It's not significant to Apple's sales numbers.