Yes, if living in Canada and hence you have the three plus years in last five in-country, you can apply- the PR card itself doesn't affect it. My 'probably' was only referring to the other criteria (which you seem to know about).
Note, citizenship applications seem to be taking a long time; if you have any plans to travel, you should apply for a PR card as well, you'd hopefully get that faster.
You can find out more info on the citizenship application route and questions in this sub-forum:
https://www.canadavisa.com/canada-immigration-discussion-board/forums/citizenship.12/